The tempo map information (tempo and time signature) is not included in the exported midi track file.
In the work session I have Tempo: 166 and TS: 3/4.
After I export a midi track and then import the same midi file previously exported, in the import dialog appears Tempo map: 120 and 4/4.
If I modify (edit) the exported midi file with the correct data and import it into Ardour, in the import dialog the Tempo map appears: 166 and 3/4.
From Standard MIDI Files Specification
In a MIDI system with a computer and a SMPTE synchronizer which uses Song Pointer and
Timing Clock, tempo maps (which describe the tempo throughout the track, and may also
include time signature information, so that the bar number may be derived) are generally
created on the computer. To use them with the synchronizer, it is necessary to transfer them
from the computer. To make it easy for the synchronizer to extract this data from a MIDI File, tempo information should always be stored in the first MTrk chunk. For a format 0 file, the tempo will be scattered through the track and the tempo map reader should ignore the intervening events; for a format 1 file, the tempo map must be stored as the first track.
It is polite to a tempo map reader to offer your user the ability to make a format 0 file with just the tempo, unless you can use format 1.
All MIDI Files should specify tempo and time signature. If they don’t, the time signature is
assumed to be 4/4, and the tempo 120 beats per minute. In format 0, these meta-events should occur at least at the beginning of the single multi-channel track. In format 1, these meta-events should be contained in the first track. In format 2, each of the temporally independent patterns should contain at least initial time signature and tempo information.