Here is a visual look at a Campangolo (left) and Shimano (right) 11 speed cassette. The short story: These two cassettes should be interchangeable giving Campagnolo riders more cassette size options. It could also mean people with wheelsets where there will be no 11 speed Shimano option (like all Zipps) could use the Campagnolo conversion and run a Campangolo cassette with their Shimano 11 speed drivetrain.
Measuring cassettes is hard work – the tapered and shaped cogs mean it’s hard to find a consistent reference point. Instead I thought a visual comparison would be easier – this is taken with the longest lens I have (150mm) to reduce lens curve as much as possible, and is inline with the top two cogs. The two parallels which the cassettes are resting on are not square to the camera because they need to support the 25t Campagnolo cassette cog and the 11t Shimano. Both cassettes are fitted to freehub bodies and torqued to spec to ensure they’re suitably compressed.
I’ve got a fascination with interchangeability between different brands and models and went so far as to put together a drivetrain calculator website which currently works with 551124 possible combinations, however is a little out of date and needs some time to bring it into the 11 speed era.