Legally you have no protection because you are not currently employed at the pool company.

Some companies may honor your pool status, and give you an available class date post-MOB...you'd have to ask them about that (not sure I'd want to have that conversation though).

I would ask the military for a deferral on the MOB, this is certainly the kind of life situation which *should* qualify. The demand signal for MOBs is pretty low right now, it's not like they won't be able to find someone.

If it's a good legacy airline job, I would pull out all stops to avoid the MOB. Unlike AD, the reserves will not provide for your family in the long run so you need to take responsibility for that. It's not reasonable for them to expect all reserves to be available 100% of time...this is one of those times, so don't feel bad about it.