They went to the trouble of using Campy Triomphe for everything else. I would suspect the bb to be a replacement. It is after all, a consumable. BB wear out. PO probably saved a few $$ using Shimano instead. Bike is almost 30 years old. Parts get replaced, and Shimano parts are the most common (and often, the cheapest).

With the rest of the parts being Campy, I bet Univega got a smoking hot deal on the parts, so the savings by substituting a Shimano bb would have been minimal. But hey, Univega is long gone, they never made a bike, so who knows?

Check the clearances between the crank arms, small chainring and the stays. POs often use bb with the wrong spindle length. I had one recently with a 127mm spindle that should have had a 113mm. One of those bonehead prior owner's moves. Needless to say, huge freakin' clearance between stays, crankarms and small chainring.

Never assume just because a part is a certain size that it is the "right" size. POs often grab whatever is handy, whether it is suitable, the right size, or whatever. Even your fireman may have swapped it out (some flippers have a pile of spares, and sometimes use whatever is closest that they have in hand).