As far I can tell the regional video options in UnleashX only apply to DVDs not games. Once you've region changed to NTSC using Enigmah nothing you can set there seems to apply to games.
How would you tell anyway unless the TV itself didn't support the output? PAL60 is 480i/60Hz is to all intents identical to interlaced NTSC. To be honest I've never been quite sure how the UnleashX dash's regional options function or are meant to function. When a PAL console is region changed to NTSC selecting PAL there doesn't appear to change the output to 576i, at least not for games.
As I understand it 480p, aka NTSC prog scan, and 576p, aka PAL prog scan, are universal standards. The refresh rate the prog scan uses is not universal (there are several standards) but that's not important for this discussion. What is, is that the output resolution has to be supported by the game/DVD, console and the TV of course.
Maybe it's possible to force a Xbox PAL game or DVD to display in 576p/50Hz (Hex editing?) but it's not a resolution option provided by the UnleashX or MS dash. You certainly can't just switch on PAL prog scan which it sounds as if you're hoping you might be able to do.