My dealer contacted Continental before fitting - The Road Attack and Sport Attack are recommended fitments for the K1200GT. (Confirmed on their www site)
The Sport Attack does not need a special fitment and the standard tyres can be fitted.
The Road Attack is recommended to have a front tyre specific to the K1200GT but the rear is standard.
Both tyres have the same speed load rating.
I always question the need for special fitment tyres and I would ask any tyre manufacturer what is wrong with their standard tyres if they don't work on a K1200GT or similar.
Take Bridgestone 020's - the 'U' (universal) tyre can be fitted on most bikes without problem yet they specify specific tyres for many bikes. These are often a few pounds more expensive - for what. Your choice.
Some bikes need a specific tyre to deal with weight or handling problems such as an LT, Goldwing, or Pan European ST1300.
UK cost fitted and balanced on bike = £215