no it wont, i tried it just because and it sits up and out of the well so the cover wont fit over it. im not certain on the tire size i tried to shove in there but it wasnt going without a fight or a flat.
I do know th e16's won't fit in the whole. It will fit fith some finess but as stated the tire keeps the cover up. The 15's should do the same.
If you want a larger spare the SVT focus has a 16" spare. It is skinny and therefor the cover sits flush. I tryed to steel.....err. I mean borrow one but Buddy would not turn around...