Hi varun01124,
The short answer is: no, there isn't any foreign ID space for which we can guarantee complete mapping.
We work separately with each provider to keep data synced, and a number of factors affect to the coverage of each partner ID-space, including:
- How frequently we get updates when the partner gets new / changed content
- Whether or not the provider has audio. (Where catalogs have audio, we can user fingerprinting to match up songs to EN IDs. Where there's no audio, like Musicbrainz or Musixmatch, we rely on string-matching on names. This is imperfect, because there are often minor differences in song titles, or even artist names.)
-Eli