Ennek a környéknek olyan jó a tömegközlekedése, mint a másiknak.

Because this sentence does not use this neighborhood as a plain subject. It uses it as the possessor of tömegközlekedése.

So the idea is structurally like:

• ez a környék = this neighborhood
• ennek a környéknek a tömegközlekedése = this neighborhood’s public transport

In Hungarian, a possessor is very often marked with -nak/-nek, so környék becomes környéknek.

Also, when a demonstrative goes with a noun, Hungarian normally uses:

• ez a környék
• ennek a környéknek
• ebben a környékben etc.

So ennek a környéknek is the correct possessed/oblique form of ez a környék in this structure.

This is a very common Hungarian pattern: when a demonstrative modifies a noun, the demonstrative usually matches the noun’s case.

Compare:

• ez a ház = this house
• ebben a házban = in this house
• ezt a házat = this house (object)
• ennek a háznak = of/to this house

So here:

• ennek matches
• környéknek matches

This doubling is normal Hungarian grammar, not emphasis.

It is:

• tömegközlekedés = public transport / public transportation
• -e = third-person singular possessive suffix, here meaning its

So:

• tömegközlekedése = its public transport

The possessor is the neighborhood:

• ennek a környéknek a tömegközlekedése = this neighborhood’s public transport

Hungarian usually puts the possession relationship on the possessed noun itself with a suffix, instead of using an English-style of.

Because Hungarian often uses the definite article with a possessed noun when the thing possessed is specific.

So:

• a tömegközlekedése = its public transport

This is very natural Hungarian. The article does not mean the possession is separate from the suffix; both belong in the structure.

A very common pattern is:

• a háznak az ablaka = the house’s window
• a városnak a központja = the city’s center
• ennek a környéknek a tömegközlekedése = this neighborhood’s public transport

Here olyan ... mint ... forms an equality comparison: as ... as ...

So:

• olyan jó ..., mint ... = as good as ...

This is one of the standard Hungarian ways to compare two things as equal in some quality.

A few similar patterns:

• olyan magas, mint... = as tall as...
• olyan gyors, mint... = as fast as...
• olyan jó, mint... = as good as...

In other contexts, olyan can also mean something like such or that kind of, but with mint in a comparison, the as ... as ... meaning is the important one.

Yes. Ugyanolyan jó is also possible and often sounds even more explicitly like just as good / equally good.

So you could also say:

• Ennek a környéknek ugyanolyan jó a tömegközlekedése, mint a másiknak.

Both are natural. Very roughly:

• olyan jó ... mint ... = as good as ...
• ugyanolyan jó ... mint ... = exactly / equally as good as ...

In many everyday situations, the difference is small.

Because Hungarian word order is flexible and often reflects topic and focus, not just subject-verb-object patterns.

Here the sentence begins with the topic:

• Ennek a környéknek = as for this neighborhood

Then comes the descriptive part:

• olyan jó a tömegközlekedése

Putting olyan jó before a tömegközlekedése is very natural when the quality is being presented as the important point.

Both orders can be possible in Hungarian, but they do not always feel identical in emphasis.

You can think of this sentence as something like:

• As for this neighborhood, its public transport is as good as the other one’s.

Also remember that in present-tense third-person sentences with an adjective, Hungarian has no expressed verb for “is”:

• A tömegközlekedése jó. = Its public transport is good.

So the structure may look unusual from an English point of view, but it is normal Hungarian.

Because Hungarian often leaves out repeated material when it is obvious.

Here a másiknak means roughly:

• the other one’s
• or more literally, of/to the other one

The omitted noun is understood from context: another neighborhood.

So the full idea is something like:

• ... mint a másik környéknek (a tömegközlekedése).

Hungarian does not need to repeat everything if the reference is clear.

Also, másik can function like a noun by itself:

• a másik = the other one
• a másiknak = the other one’s / to the other one

Formally, it is the same ending as the dative, and many grammars describe this as a dative-marked possessor.

So in function, here it is about possession:

• ennek a környéknek a tömegközlekedése = this neighborhood’s public transport

But morphologically, the ending is the same one you also see in ordinary dative uses:

• a fiúnak adom = I give it to the boy

So the short answer is:

• the form is dative
• the role here is possessive

That is completely normal in Hungarian grammar.

Because Hungarian usually marks possession in two places:

1. the possessor may get -nak/-nek
2. the possessed noun gets a possessive suffix

So instead of an English-style pattern like:

• the neighborhood’s public transport

Hungarian tends to build it as:

• the neighborhood-DAT the public transport-its

That may seem strange at first, but it is one of the core patterns of Hungarian possession.

Very often, the possessed noun is the most important part to look for, because that is where the possessive suffix appears:

• háza = his/her/its house
• autója = his/her/its car
• tömegközlekedése = its public transport

Yes. In Hungarian, the verb to be is normally omitted in the present tense, third person, when you are simply saying that something is something or is some quality.

So:

• A környék csendes. = The neighborhood is quiet.
• A tömegközlekedése jó. = Its public transport is good.

That is why:

• Ennek a környéknek olyan jó a tömegközlekedése, mint a másiknak.

is a full, normal sentence even without an explicit verb meaning is.