Traktor uses XML to store metadata. Currently MIXXX imports the filenames, but not the cue points.
There are several programs that are able to achieve this conversion. The most complete programs are proprietary and for MacOS only. Windows users and/or opensource is a lot more limited.
All the above converters, and probably MIXXX in the future, are susceptible to the following issue: For some mp3s, all cues will be shifted in time for a constant number of samples. This issue depends on the actual decoder definition of the 00:00:00 time point ( more info here)
Only some converters specifically address this issue. Known successes are:
The other converters have been confirmed to be affected by this issue.
update: some research hints this issue is correlated with the specific LAME encoder version: https://github.com/digital-dj-tools/dj-data-converter/issues/3
Some Windows users are able to convert their collections using MacOS VMs. The simplest method uses a full import/export to an external drive. This is dramatically slow. A faster method uses an internal network share, but it requires manipulation of the XML libraries. That extra step can be made manually, or be scripted as well.