Interesting question.
I do not have the answer to it, but only some clues:
- Tom's Diner is a Suzanne Vega song which original version is under (c) A&M Records 1987 (lyrics rights belong to AGF usic & Waifersongs Ltd).
- I think that all versions used on the Tom's Album are bootlegged versions without any prior permission.
- Credits of all versions go to Suzanne Vega (and in some cases to a co-author).
- Tom's Album is under (c) A&M Records.
- DNA appear courtesy of EMI Records (UK).
Conclusion: I guess Tom's Album is under exclusive A&M (c) with a posteriori permission for all bootlegged versions to be exploited under their own licence (when there is one).
Of course, this is only a guessing. I suppose the exact answer can be found somewhere...