Looks like the 2017 update of premiere plays back the LT codec except that UHD comes in at 3840x1080/.5 pixel ratio. I will check HD files once I get home and see if they are working with this new update.
Solution: Create a timeline in 1920 x 1080 or 3840 x 2160 before dropping any LT-files on it. That is, don't create a timeline by dropping LT-files on the Timeline-window.
I haven't tried this out yet, since I haven't upgraded my Premiere, but according to my contact this should do the trick.
Just picked up a Varicam LT myself, and when I posed this question to the guys at Panasonic, they recommended the Adobe LT plugin from Calibrated Software:
I have Premiere Pro 2017 but have not personally loaded any AVC Intra LT clips into the timeline yet. Will check it out once I get my Varicam or lay my hands on some footage.