My understanding is the Bc5 lines were not fully developed until after Kasparov had quit playing the Scotch and that they changed the eval greatly. It does take into account Gari's 5. Nxc6 which seems in fact to be the only line which gives White anything to hope for. All in all, good for OTB but probably insufficent for CC. By that token the King's Gambit can also offer some opportunities.
As with you, what I've read rather than being able to offer a qualified opinion myself.
Aye, I ran some database numbers and came up with the following.
The Bc5 line scores:
37% win for white
39% draw
24% win for black
An instructive game on this line might be Kasparov - Yusupov in Horgen 1994.
I'm not sure about the other lines but I compared it to ruy lopez in general wich scores something like:
39% win for white
36% draw
26% win for black
By the looks Scotch Game seems more drawish but with similar win/loss ratio.
I'm not sure about how the Scotch holds up in CC though.
I dont think I have played the scotch with 4 Nxd4 as white yet but have faced it as black. I always play either 4 Bc4 or 4 c3 when I play scotch..... :-)