I understood that the airport charged the airline for providing these services and Ryan used to charge the the RPM pax the cost + some, until the court case some time back. We all know Ryanair are a cynical bunch and they know that RPM pax slow down turnarounds, trying to get off a "wheel chair R or C" as they are know in the trade means that you cannot turnaround an aircraft in 25minutes at most places.
RPM =Reduced Personal Mobility
C = Cant walk=lift off
R= Can make the steps but not walk to arrivals
The new regs require airports to provide care from car park to aircraft, and about time too!! i wish they would do the same for aircrew