Yes! A sample license covers remixes of your derivative (new) song with samples from Tracklib, but remember that the remixes, just as your original mix, need to be registered with a Collective Management Organization so the revenues made from the remixes can be accounted for (and royalties paid out).

If you make a remix of your song, you should register it was a version under the same license. 

Note that you cannot make a remix of the original songs in the Tracklib library.