as you know it was initialy developed for the military quick installations.operated in the uhf range and didn't suffer the terrain concerns as did ILS glide slope signals.In Canada there were 2 installations one on the prairies, one north of Vancouver in the mountains.Both worked well,but as the original promise of low cost dematerialised ,and the concern of frequency congestion/FM station interference was overcome the Industry saw little benefit with the retooling costs.Now GPS has pushed the use/interest of MLS out of the picture..
There was also installations in YUL/YYZ with the downtown intercity project.These worked well wth twinotters and a 'steep' glide slope.After proving its sucess this project was discontinued by the Federal Govt...