They all use slightly different actuation ratios, but for all intents and purposes SRAM and Shimano mix and match without any problems, but Campag does not play very well with either…
However, as mentioned above, the JTek allows mixing various components, plus CRC have some funky Ambrosio cassettes that allow you to run Campag ergos/rear mech with Shimano wheels and vice versa, which might help with things…
But, unless you have some need to, why not just stick with one manufacturer, then you know it’ll all work fine…
I looked into this as I’m *fingers crossed* getting a Roadrat on the B2W scheme and wanted to transplant my Campag stuff onto it, while still running the cable discs, which is a problem as getting hold of Campag compatible disc hubs is expensive! That was when I discovered the Ambrosio cassettes on CRC, which seems a far better(cheaper) solution for me!