There appear to be 2 very similar R2 Japan releases with a 5.1 DTS track.

1. PIBF-1219: http://www.hmv.co.jp/artist_%E3%82%BF%E3%83%BC%E3%83%9F%E3%83%8D%E3%83%BC%E3%82%BF%E3%83%BC_000000000115097/item_%E3%82%BF%E3%83%BC%E3%83%9F%E3%83%8D%E3%83%BC%E3%82%BF%E3%83%BC2-DTS_566051

2. PIBF-91219: http://www.hmv.co.jp/en/artist_SOUNDTRACK_000000000115097/item_Terminator-2-Judgment-Day_1987310

I own the 91219 release but have never seen the PIBF-1219. I am convinced that is the same release as PIBF-91219 but 91219 has a slip case. They seem to be identical specs but DVDCompare states there should be a commentary track on the disc which is nowhere to be found on 91219. There is only an .ac3, .dts, and a Japanese dubbed stereo track. It seems that the 5.1 DTS track in question here comes from these 2 releases by Pioneer. I am uploading the .ac3 and .dts files from the PIBF-91219 disc right now for review.