In early 2001, a kind person by name Richard F. Nagel recorded several of the Transport Tycoon tunes on a SoundBlaster AWE32 card with a large RAM expansion and some just as large sound banks.
The original site these files were posted on is long gone, but at least the MP3 files are preserved here.
If you search for it, you can find the old discussions around these files in the AGMTT archive on TT-Forums.
Unfortunately, one file is missing. In one post, Nagel mentions having uploaded 8 files to his site, but my archive only contains 7 of them. If anyone has a copy of the missing recording, please do get in touch.