Good eye and good muse there, Cat, regarding the proposal of stations being allowed to raise power until some absent 'dominant protected' stations finally made up their minds.
I'd asked some time back if US stations on 690, specifiaclly, could get some nighttime elbow room when the French 690 in Montreal left the air. I was told 'no'; a treaty is a treaty.
And certainly, US daytime stations on 690 and 940 knew what they were getting into back in the Sixties when they signed on within the extant rules .... WINE 940 Connecticut .... WXUR 690 Media PA ..... WADS 690 in CT ....
(Even new stations on the USA-cleared 1520, such as WCHE in PA, WVOB in MD, WSLT in South NJ and WTHE/WFYI on Long Island knew the daytime-only drill and accepted it; WKBW would take over the frequency at night. Period.)
I doubt that any US station currently licensed to 940 or 690 with, as you say, '1 to 10 watts' is going to see any certifiable financial upswing by increasing nighttime wattage. Heck -- if 'CBM 940' is having problems with the electric bill, where is the hope for any other station?