I've had a couple of jobs covering for other firms, Borough Cabs being one from your neck of the woods BS. If a set fare is revealed it's usually as a comment on the offer/job screen above the address. I don't accept those fares and I have had to return one client to T2 when he insisted that he had a set fare agreement that hadn't been communicated to me. Another conceded to paying full fare and pursuing the difference from the firm he booked with.
However, the €11/€15 options presented last night were built in to the mytaxi software so I'm inclined to suspect that it was a limousine job as suggested by JM. Why such a fare would come through to a 9 year old Octavia in desperate need of a wash is a mystery. I might have to ask the depot.