Campy square-taper cranks and bottom brackets use the ISO interface - most others (including Shimano) use the JIS interface, which has the same taper angle of 4 degrees but is slightly thicker. You can mix them in practice, but it ain't close to ideal.

Note that the square-taper interface is different than the threading of the bottom bracket.

Different cranks get proper chainline with different bottom bracket spindle lengths. It's worth trying to figure out what bottom bracket spindle length is ideal for your crankset.