There are clearly some caveats around the scheme, as EK points out....however, I think in fairness to Oxford they've done their best to remove those problems - in that they'll convert you to an fATPL course if it does go tits up.
MPL at 1500 hours I think I'm right in saying becomes an ATPL, the same way an fATPL matures, so once you hit that, you're laughing. The danger would be if you got taken on, got to about 7/800 hours and THEN FlyBE went under...doubt OAA would change your qual at that point - so you'd be stuck with some conversion work....SOME financial cost, but mainly the pain in the ass of it.
However, all told, right now if you CAN get on an airline mentored scheme of any sort, then it is by far the safest route. FlyBE seems an excellent company with strong business model....really not a bad bet in my book