That's because Fomapan doesn't work well in the D-94A process that every other black-and-white reversal film uses. It worked with the original D-94 process, but the new chemistry gives it that mottled look. That's why it's so hard to find a place that processes it.
Apperently there is an issue with the Bleach from the new process not working at normal times. NCL did a roll of 16mm for meabout a year ago that came out brown and mottled, and they said that the process will need adjutments. I would sugest contacting any lab you plan to use and asking them if they have the process changes down on FOMA yet. B&W Film Fcatory in Toronto used to charge Extra to do the Foma, but they have now closed down.
I have Just sent a note to NCL to see if they have the process down yet.
http://www.niagaracustomlab.com/
UPDATE: The Replay I recieved is that "we are running this process without a problem
this bleaching problem was happening because kodak changed the entire process a couple years ago
so it would not work with anything except their new stock
we have since adjusted their formula to handle other stocks as well
and have tested the foma as well as agfa , orwo and older kodak stocks all with success"
So Looks like Foma R-100 Processing in Toronto is back in business.