I really do not see this being a union issue. 10:30 end time scheduled, 10:30 end time kept. Union or non union, you could get the same result...
I've finally done a trade show in a non-union environment, sooo soooo soooo sooooooooooooooooo much nicer, but in this case, its the fault of the people putting on the event giving a 10:30 cut off, when all the songs from all the musicians and stage switch out time goes past 10:30...