When you upload music tracks (via Music Manager), how do you think Google works out if they already have the track and just add a marker in your collection and when they have to physically upload the whole file?

As I take advantage of the 50k limit, I'm finding surprisingly large numbers of files that need a full upload.

One thing I'm curious about here. I upload a track Google hasn't seen before so it needs the full upload. Some time later, SWIM uploads the exact same track and file from a different PC to a different account. Does Google recognise it the second time around and not bother with doing the complete file upload again?