I recall a Model Railroader article in the 70s (?) that showed an engineer moving the throttle lever in the cab, and also the O scale loco had separately operating reverse gear linkages.
I believe you may be thinking of the radio controlled O scale model of the CB&Q 5632 belonging to Mr. Howard Bixler. If I recall correctly, the locomotive was a heavily modified Max Gray model. It featured an impressive array of moving parts including the Engineer figure. I had the good fortune to see and tape Mr. Bixler's locomotive in operation at an O scale national convention during the early 90s. I'd be curious to know where that model is today as the owner was up in years.
A few pictures of the locomotive and one of Mr. Bixler himself are posted below.
Bob