I'm sealing up some holes and gaps in my attic and dutifully using fire block caulk where some electric cables are coming through the studs and gaps. In other locations, I'm using Great Stuff like spray foam for simple air gaps. However, a couple of hard to reach places make spraying the foam difficult. It would make the job easier if I'm allowed to foam over the fire blocking caulked holes and gaps where the electric cables are coming through.
The entire point of the fire blocking foam is prevent/slow fire from spreading from one area to another; it has less to do with the electrical/plumbing between two areas than the hole that was created to allow them through. As long as you have fire grade blocking to the prescribed thickness, there is no issue with other foam on top of it.