I'm familiar with the TLDX covered hoppers leasing to private name companies, but have never seen the intermodal equipment. Was it a (much) smaller operation than the covered hopper leasing. Where did they run is what I am wondering most, as I've never seen a photo or read written mention of the cars.
Since Pullman leasing basically ceased operating in the late 1960's (1968?) before TOFC became as dominant as it is today the TLCX leasing operation was relatively small. And since Pullman leasing was winding down as Trailer-Train was growing TLCX was never a real player in the TOFC market.
As to where the cars ran and who leased them, without access to Pullman's Leasing records only a guess can be made that the rr's that were customers of Pullman's passenger car leasing program were likely customers of the freight car leasing division. So the cars could have been expected to appear anywhere. Maybe someone has done for the freight cars what Jerry LaBoda has done for the Pullman passenger car leasing fleet but I am not aware of anyone that has done so.
The reporting marks were/are TLCX not TLDX - The leasing operation in the 1960's was spun-off into Pullman Leasing Company - PLCX reporting marks added. In 1981 it was purchased by Intel and now is part of GE leasing. With TLCX and PLCX reporting marks still being used on equipment.