Diesel Generator Dummy Synchronizing

See "Chernobyl"

This accident was caused by people without proper training.

So you want to know what happens if you close a generator on to a dead bus using a synchroscope that is being fed from another source. The answer depends upon how detailed your simulation program is regarding things like the generator, prime mover, governor, automatic voltage regulator, protective relaying, balance of plant, etc., etc.

If you would like further feedback why don't you tell us what you think will happen and why, then we'll have a basis for more discussion.