Text chat is built into Motor Town — there's an in-game chat window that, among other things, broadcasts personal-best and lap-time notifications.
No in-game VoIP
Voice chat is not currently supported in-game. Players use external voice tools like Discord. Proximity chat has been a recurring community request but is not in the game as of writing.
TinyTown server
TinyTown's recommended voice channel is the community Discord — see the TinyTown #voice channels for the active stage and patrol rooms.