I think it would depend on the type of load?
Purely resistive, passive inductive, AC motor, rectifier etc??
eg. A symmetrical resistive load would probably take roughly 15% less current on the remaining phases and feed the average of the two voltages back on the broken wire.
An already running three phase induction motor could keep running as long as the load was not too high, and return near the original voltage to the broken wire.
A similar motor attempting to start after the break occurred would take many times its normal rated current.
(And if anything has a neutral connection, it changes again..)