Small condo building. There appears to be issues with some unit water lines are not connected to the correct individual water meter?
Is there a method of sending a signal down the line to verify?

One way is to turn off each meter one by one, and see who doesn't have water? If you are going to be home a while and don't need water, turn off and see if someone turns it on because they lost water? It is also possible for someone to tie onto some one else's supply line. If you suspect someone, turn off your water when they are in the shower?

Your building manager can call the water company or the appropriate entity. How does your lease say you should handle this issue? What has raised these concerns?

As suggested above, find out by method of elimination. Quick, clean, easy, and precise way of finding which meter services each condo

Milo