No, you can't say "a-t-il un bureau de poste près d'ici" because that mean "does he have a post office near by". ("a" = "to Have" in the present, 3rd person. "il" = "he" when with the verb "to have", not the impersonal "it") Some people say "y" mean "there" but it's not really how it works. Imagine "y a-il" as an expression. You need those 3 words together to make "is there... ?". Same with "il y a" (the answer) you need the 3 words to make "there is..."