The answer is probably no, with a two limited exceptions. It can of course import from the last xml version of BTB (v 0.4.something), and from .kml files (which just produce a track).
If you're asking if it can import tracks from other formats, like rFactor's or some 3d program, no it can't. A track in rFactor format, and no doubt most others, is just a load of polygons and materials, along with checkpoints and so on. There's no way those polygons could be converted to BTB format.
In BTB, the track is represented by nodes, control points, surfaces, widths and cambers, from which the track polygons are calculated. The terrain polygons are of a different nature to the track, and some of them are anchored to the track (and some aren't), as are objects and walls. Imagine trying to write a program that could take a load of polygons and work out which ones represented the track (and could calculate good locations and angles and distances for nodes and control points), which ones represented the terrain, objects, walls etc.