I would be absolutely shocked if that thing was compatible with any sort of standard bottom bracket. You usually can't even mount a standard bike seat on those stationary bikes without a $100 adapter from the manufacturer.
And the worst part is, because they don't use standard parts, they're more prone to failure, because these manufacturers aren't masters at making bottom brackets and cranks the way, say, Shimano is.
As for solving the problem, I see that the whole bottom bracket and bottombracket shell assembly appears to be welded into the frame. Can such a thing be de-welded?