forgive me, but don't you have to take the ATP test in a plane with a controllable prop and retractable gear? while you can take some of the test in a fixed gear/fixed prop plane, you have to demonstrate the above retract and controllable prop.
In the US you have to have 10 hours training in a complex airplane to get a COMM certificate. (There's a reason for CE182RGs.) And you have to have a COMM to get an ATP (military excluded.) The other 1490 hours can be in a CE152.
Back more than a few years ago my ATP written was about to expire. Did a SEL ATP checkride and was running around for a while with an ATP SEL COMM MEL DC3 till I could do a multi checkride with someone who could give the ATP MEL.