As a semi-related aside for the future, AF/KLM take control of tickets coming back from Europe at T-48, not at T-24 -- which is problematic if you are an FO/GM since it requires you to get manually assigned to C+ at CDG/AMS (because AF/KLM take control before the GM/FO window opens up to clear you automatically).

The TA/DL charge for taking over before T-24 is also dictated by your company's relationship with DL. When I book for work via our TA (AMEX GBT via Concur), I don't encounter any charges for DL to take over the ticket or process changes before T-24, however United does charge this fee (have been hit with it when doing cash upfares on UA -- where DL does not charge to take the ticket over and upfare me) so I think this is one of many things that can be negotiated depending on how much leverage your company/TA have.

And I do agree you should have been notified via your TA. I know when I've been upgraded at the PM window because I receive a MAJOR FLIGHT CHANGE email alert from AMEX GBT before the DL app sends me the upgrade notification ribbon on my phone -- and of course they send emails and texts when I've been delayed offering to assist me with re-booking (though 99/100 times it's faster and easier to go via the DL PM line)