I had a Bianchi Snark, which has very similar dimensions as far as frame/swingarm etc...I put Sava b8 2.25 x16's on my wheels, and they BARELY fit, the chain almost grazing the sidewall even when adjusted properly. Those are relatively narrow even for a 2.25, your average 2.25 tire like the Sava MC2 that you'd find on tomos would not fit at all. Therefore I'm pretty sure a 2.5 tire of any kind would not fit.
I mean, I may be wrong, but these minarelli/morini step through frames are usually very similar, sometimes exactly the same.