Can a broiler function as a grill substitute when making kebabs?
The first thing I have to say is kebabs and overcooked are synonymous. If you want all your meats and/or veggies to be cooked right, I would advise you to put each item on it's own skewer so you can take them off as they are finished.

As for a broiler and broiler plate functioning as a substitute for a grill, I would say that it won't be an exact substitute, but you will at least get the high temperature cooking and caramelization you would expect from a grill (you will just be missing the smoke flavor).