It's not that I have problem transporting special units or military units by transport ships. The question is, for example, in single player campaign for romans, when you want to colonize an empty island that has some resources scattered around, how to you transport builders and diggers to that specific island. I was able to move special units with military, but not builders nor diggers, and because of that, I can't build there anything at all. Is there any way to do so?
Okay, somehow it never occurred to me, that I just can change settlers into Pioneers, then transport them to the island, and then, change them back onto normal settlers, where they on their own change either into carriers,builders or diggers.
Correct - You must transport Shovels/Hammers on Trade Ships and Pioneers on Transport Ships.
This is the only way to fully colonise another island (to build buildings, that is...)
Great if you're in a 3v3 or 4v4 Random online and the opponent is looking for your last guard tower for over an hour Much fun!