I just received a rental copy of this today. As someone who's authored and encoded DVDs, it is my opinion that the source looks like a processed standard-def studio tape (and not a very appealing one, either): that is, marginally better than DVD, but way below 1080p standard. The film grain structure (or what's left of it) is thick and clumpy, it looks undoubtedly SD.
If Optimum are reading this, I urge them to look into it. Did the master tape come from France? Could there possibly have been a language barrier issue? For example, if Optimum requested an HDCAM SR tape of "Escape from New York", the facility could have made them one, using a Digital Betacam tape as a source. Optimum receive the HDCAM SR tape and make a disc out of it, completely unaware of the original source material.
Blu-ray Disc (and DVD) Compressionist/Author
US Correspondent & Tech Consultant, HDTVtest
ISF Certified Calibrator (Level 2) / THX Certified Professional (Video Calibration Level 2)