Yes! A sample license covers remixes of your 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 any remixes, remember to send us the song titles, artists and ISRCs specific for the remixes to us as well as the Original mix. And don't hesitate to contact us with any questions you might have. Note that you cannot make a remix of the original songs in the Tracklib library.