Is the Tracker able to import and export classic mod files?

Polyend Tracker is able to import/export classic tracker project files with their basic properties (samples/instruments, notes/patterns, song structure, and volume info). Open .mod/.it (many other classic tracker project file formats like .xm/.s3m can be opened in the Schism Tracker or Milky Tracker and then converted and saved as .it and so imported to Polyend Tracker). It allows you to export .it files that are compatible with the Renoise, Schism Tracker, or Milky Tracker. 

Note: The .mod file import and .it export may not 100% flawlessly work as expected.

Accomplishing full unity in terms of exports and imports is not fully doable. Even considering a standardized level of compatibility, it won't be possible to convert or provide data to convert projects one to one. There’s a variety of tracker applications out there, they're working on a different basis usually. And that’s also why the import/export capabilities are limited to the currently supported parameters and values.

In other words, you may need to adjust the instruments and their particular values, maintain samples and volume levels manually.