A maglock does not interfere with the latching operation of the hardware, or interfere with the ability of the door to withstand fire.
I would guess that a maglock rated for a fire rated door is similar to blue or red e rated for a fire rated door, it doesn't effect it.
If you are using them in place of the postive latching device I would say you can not do it, because once the mag releases sometimes they do not latch back and also they have not been tested as an assembly with the door when it got the rating.
Another consideration is the location of the door in relation to the egress. If its located in an egress path, then a variety of Building Code requirements become applicable
