Was that ever released for film use? I don't recall seeing any prints referring to ProLogic or ProLogic II during my time as a student film projectionist. If so, it was highly backwards compatible since our decoder was only SR (analog 4.0 matrix).

The prints would generally come with SR (analog 4.0) and SR-D (Bitmaps between the sprockets). Most of the time you'd also get DTS CDs and about 40-50% of the prints we got (in Stockholm) had SDDS, though I think there were maybe like 5 SDDS theatres in Sweden.