Yes, X-plan pricing is based on A-plan + a certain percentage.
The Volvo A-plan pricing isn't as much of a discount from MSRP as a "full" Ford vehicle, so the X-plan price isn't as far off it as the Ford vehicles.
For a lease, everything is determined from a vehicle purchase value, which is normally started at MSRP, but for X-plan, it starts at the X-plan pricing. Everything else works the same, with the only ultimate differance being the monthly lease payment is less.