I've been researching Systainers and inserts before a big buy in the next few days, from what I understand the Classic inserts are compatible with the New T-Loc so it would follow that inserts are interchangeble.. Hope this helps!
They will fit with some modification. Its really easy to make them fit. I use a dremel tool with a sanding drum attachment to take a little bit at a time. I bought the tanos fein insert and put it in a classic festool systainer.