nismosr - what are you actually trying to do?
68mm shells are 68 mm-ish, Campag's tolerance is the same as Shimano and SRAM, +/-0.8 mm so given cups and BB, the crankset will fit.
If you are looking at using Overtorque threaded cups with Vuma or THM, you may see a couple of issues - taking up any inaccuracy in the BB shell width is one, as Campagnolo use a threaded expander for this job in OT and that may and may not work with the cranks that you mention (there needs to be a flat interface available on the back of the crank), plus if there is differential in axle length (possible but not that likely as OT works fine with a bog standard BB30, BB386 and BB30 PF frame, using it's own cups), the amount of adjustment in the threaded expander may not be enough.
Campagnolo kit is generally compatible with other manufacturers to the same limits as other makers are cross-compatible (or indeed car manufacturers, or hi-fi makers or flat pack furniture makers or any number of other things you could name are). The problem always comes, regardless of whose kit you look at, when you try to do things that are outside of the manufacturers range of tolerance or expectation. It's not a question of "bothering" ... it's about some pretty basic engineering concepts and how different makers choose to address the competing demands of USP, price point, material, costs and durability.
I wanted to get the OT crank for a threaded BB frameset but since campy I think does not carry a threaded English BB for OT, I'm looking at other alternative solution like using different brand BB that uses 30mm spindle.