Are Campagnolo cassettes interchangeable?

Yes they are. The 11 speed cassettes of Shimano and Campagnolo have the same sprocket spacings and overall widths, so you can swap a Shimano wheel/freehub/11sp cassette with a Campagnolo wheel/freehub/11 speed cassette.

Can you use Shimano cassette with Campagnolo?

Read this article, all 11 speed cassette works with all Shimano, SRAM and Campagnolo drivetrain, meaning chain and RD and crankset, so the answer is the Shimano 11 speed chain and Campagnolo 11 speed chain are interchangable.