My BMW dealer is 110 miles away so I took my 2011 in for new rubber at the Honda dealer. I found out what brands he carried, looked online for the costs and he matched it, plus tax of course. I couldn't find any reviews for the ContiMotions on an RT so decided to give them a try. So far they grip great even on cold wet roads, are wearing very well, I'd say at least 6k, which is good because the Bridgestones only got me to 4200 miles before they needed changed.
I have a set of PR3's waiting to go on, the rear is the "B" because I ride loaded a lot. I'm hoping to get at least 10-12k from them on my AK trip in June.
I've never had any issue mixing and matching tires and found some combinations work better than matching brands, so you should be fine.