Given what has been mentioned above, is it surprising supermarkets don't really use RT much? Why would they saddle themselves with additional cost for a brand that isn't theirs and for which no premium can be applied?
The supermarkets sort of piggy back on it. In meat and poultry terms there are no brands in the supermarkets. It is all sold as own label. So the processor has put their RT logo onto the supermarkets own label pack. Some meat products are not supermarket own label but are brands such as within the sausage and bacon category such as Heck, Richmond, Denhay etc.. Here you may see the brand applying a Red Tractor logo should they be licensed. But for them it is all about their brand and not about Red Tractor.
Now there are some cases where Red Tractor does deliver market access. Such as within a scheme called Food for Life which operates within the School Meals market. But that's probably for another thread!