The IMDb boards are convinced that it's a rip-off of Moulin Rouge, but they're wrong. The trope of the play-within-a-play predates Baz Luhrmann by quite a bit, and that's where the similarities end. Perhaps Love tells three parallel stories: the musical being filmed, the cast during the filming, and the cast before they were stars.
It's worth another viewing or several. I had trouble following some parts of the musical numbers because of the combination of quick cuts and subtitles.
(Also, the lead boy was very pretty. Oh! He was in Chungking Express! No wonder he looked so familiar.)