Easier then you think. You know how 110 volts wall socket can share one breaker with 5 or so wall sockets. Loads are all in parallel. So for EV case you plug in up to 12 EV on one breaker. Yes you are right there is electronics that allows a part of the power to flow to each EV. Cost of that gadget is about $500 per EV, the same cost of L2 for one car. If some cars are not plugged in , the remaining ones see more power. So you just plug in and go to sleep.
By allowing fewer EV per circuit breaker the charge rate increases. So apartment owner could offer fast, medium and slow plugs with different charge rates and cost