Hmmm...I unfortunately don't recall any odd use of the LotR soundtrack.
I guess the strangest thing I've heard of that sort happened back in the late 70's before cable TV (yes, my memories go back that far

).
Back then (in the olden days) TV stations in U.S. signed off for the night with a rendition of the Star Spangled Banner, and then some inspirational moment that somehow proved that America was still a god-fearing nation. Well, anyway, this certain religious moment featured a beautiful little child in a a pastoral meadow petting a little lamb. In the background was the soothing sound of an acoustic guitar, evoking a quintessential sense of peace for the scene as a profound quote from the Gospel was reverently spoken.
That was, until I suddenly realized I had heard that tune before; in fact, it was on one of my favorite albums of the time. I was amused to no end at the thought of some wise-acre sound engineer slyly editing the music for this religious moment. The tune? Black Sabbath's 'Fluff' from the 'Sabbath Bloody Sabbath' album:
http://www.youtube.com/watch?v=CtkmRiA5UOE
Sorry for the slight departure. I figured this was the only time I would be able to post this memorable moment before...ummm...I, like, forget it again.