I do believe there are (fairly) tight tolerances for clock synchronization between the network and the user equipment/handsets, but I don't know that it necessarily involves communicating the wallclock time. And the oscillators for signal timing aren't necessarily used for timekeeping.
I get that, but often the towers use GPS disciplined oscillators from what I understand (and have seen in limited circumstances), they inherently know exactly what time it is. Seems trivial to sync that as well, just kind of assumed they did that.