I want change the groupset on my Scott Addict R2 from Shimano to Campagnolo. Is Campagnolo fully compatible or will I need to make frame changes?
I don't think you will need to change the frame, I looked at one of the bianchi series a while back and I saw the same frame (the Oltre - I can but dream) offered at different prices depending on the groupset. But the groupsets available were from both shimano and campag. There's variations with Dura Ace, Ultegra, Athena, Super Record etc. I can't imagine the actual frame would be different between these groupsets, otherwise surely it would have a different name?
Here's the link to that page: http://www.bianchi.com/Uk/Bikes/Bikes_List.aspx?RangeIDMaster=74825&CategoryIDMaster=74829
You may want to visit the Scott site, you may find something similar
However I can imagine you're going to have to change just about everything else, though, including wheels (well, as far as the freehub at least).
There are no compatibility issue at all. For the most part, Campagnolo, SRAM and Shimano have designed their groupsets to work to common frame characteristics. Drillings for electronic might be an issue in that Campagnolo EPS has until recently and still in the case of Chorus) needed an extra drilling for the Power Unit charge port, but that is a hurdle that any competent fitting technician should be able to clear.
Campagnolo make adapters for all of the current formats of BB with the exceptions of BB Rite in PowerTorque only (they do it in UltraTorque) and Specialized OSBB, neither of which is not a problem that applies here. Shimano use third party solutions - they don't offer any in-house compatibility with anything other tha BSC or Italian threded BBs.
As your Scott is a modern bike, I'd be inclined to agree with some of the other answers here and say that I don't think you will require any modifications to your frame if you switch from Shimano to Campagnolo. There are some areas which are not strictly frame related where you may need to be careful.
If you're switching to an EPS groupset then it's likely that your frame won't have specific mounts or routing for the electronic cabling. However, in my experience you've often got options to run the cables externally quite neatly.
As already mentioned, you will need to either change your wheels (or the freehub body if possible on your current set) so that they can take a Campagnolo specific cassette. If your frame was much older, I'd also suggest that you check the spacing between the dropouts to ensure there was sufficient room. One area I have run into that's worth checking, is that if you intend to use an 11t sprocket at the rear with a compact chainset (or triple) that there is sufficient practical space between the chain and the chainstay.
You should be mindful of the bottom bracket setup on the R2 and make sure that any new Campagnolo system is compatible with it, or that you have a relevant converter if required. The same goes for the front mech, make sure your new one is the same (band or braze on) as the existing Shimano one.
Again, not a problem for the R2, but if your frame was setup for longer reach brake calipers, I'd also suggest that you measure the existing ones before you order, to ensure that the new ones have sufficient depth.
If in doubt or if you want extra reassurance, I'd check in with your local Scott dealer to get their confirmation, they may also be able to offer advice on subtle changes they make when setting up for Campagnolo which will make your transition smoother.