From what I am personally aware of, FreeRTOS has no specific requirements for exception handling. However, one thing you should be aware of is that because of how the C++ standard is implemented in various compilers, it can actually catch you out when you use the C++ exception mechanism, like in this thread here from a couple of years back (though I think on that specific occasion it might have been due to a compiler bug rather than C++ standard and how its handled). There was another thread from about 6 months ago or so (not something I can immediately find for reference, will link it as soon as I find it - perhaps others will also remember it and beat me to linking to it if I dont find it by then) where this subject was touched on when compilers can catch you out with the use of C++ exceptions in FreeRTOS.
Ilya
EDIT: ah yes, it is this thread here - it does mentions the fact that you should be very weary of using exceptions for the reason I mentioned but it also mentions a few other issues you should be aware of