Yes, a bus service run by NAT still links Rhoose station with the Airport terminal. Passengers must now pay £1 each way for the trip. It remains the quickest way by public transport to/from get from the Airport to Bridgend & points west. Unfortunately, no clear signs appear by the level crossing at Rhoose station telling travellers which side of the line they need to go for Bridgend & points west / Barry, Cardiff & the east.
Last time I checked the Airport, no clear signs marked which bus stop served the different services. A bus arrived marked 'Shuttle'. I said to the driver "What Shuttle are you? The one to Cardiff or the one to Rhoose station"? He said, "neither, I am the car park shuttle". No wonder this airport is going bust!
Regarding the City Line, I don't think that ATW even produce a mini printed timetable of the entire route. Surely, they should be targeting employers near the line to encourage cross city travel? The Inland Revenue at Llanishen comes to mind along with Cantonian & The Bishop of Llandaff High Schools. Heath Hospital generates huge amounts of traffic. Unfortunately, no shuttle bus links Heath Halt with the Hospital and many won't make the 20 minute walk - especially in winter.