@ Winopener.
You just stumbled over a very little known truth, my friend!
If you use full bandwidth DTS encoding at the higher bitrate of 24 bit - then the encoded disc is as near to lossless as possible.
Your assumptions are perfectly correct. I got this information direct from the head of DTS Europe, and what happens is something like this:
Your original source material, once encoded into DTS, then becomes what is called the "Transport Stream", which as you know is at 16/44.1 for CD and 16/48 for DVD. When it goes through the DTS decoder, it gets turned back into what is called the "Payload stream", which should be as close as possible to your original source files but depth.
Using 24 bit source does in fact mean the encoded file is very close to lossless.
It actually gets a little more complicated in reality, as the transport stream isn't really at 16/44.1 at all - it is in fact at 14/(original). This is done to reduce the possible damage if the file is played by accident through a normal system with no DTS decoder - it is only the file header that is at 16 bit to fool the burning applications into accepting the file. You can also encode to DTS stereo or Surround for CD using 24/48 files as long as you tell the encoder to use a 44.1KHz header. I do this all the time in the Nuendo DTS encoder. It will happily encode to DTS-CD from a 16/44.1 file, but it sounds noticeably better if you use 24/44.1 and even 24/48 with the flag set correctly will still play back correctly.
If you like, I have the DTS specs in PDF format - drop me a mail and I will happily send you a copy.