Don't know about the TX, but with my T3 a backup is possible. I have just looked into that mentioned AminetFile, its just the modified library, but indeed it doesn't give you the whole picture.
In Trident you find under Classes the palmpda.class. Try Configure and you will see the requester for a command. This command is just a arexx-script, which will be launched in the event of a hotsync. Output goes to the Shell console window, also configured here.
Just read the description of palmpda.class in your Poseidon-E.guide, here you find also a sample arexx-script. ;-)