Ken, I touched bases with Ken Jorgensen at Ruger about your question; he was out of town, so it took a while to get a response.
Ken tells me that the Ruger LCR is good to go with any +P load, and says that since to Ruger's knowledge SAAMI doesn't provide specs for +P+, they can't warrantee for that.
I will say that Buffalo Bore is pretty warm stuff, but having shot some other brands of +P -- and some rated +P+ -- through my own LCR, I personally wouldn't worry about it.
With any handgun, of course, the more extra-hot loads you put through it, the sooner you can expect it to wear out. As the head of another handgun company told me once, it's sort of like taking a family sedan built to last 100,000 miles at up to 70 MPH, and running it constantly at 100 MPH.