I'm pretty sure they'll use the PAL masters used for the PAL THX WS LDs released in Europe.
Actually, according to another film archivist/restoration expert on the HTF, the Laserdiscs released in PAL format from the 93 masters were upscaled from the NTSC. there were no real PAL transfers. It would be the same thing here. If there were PAL masters I'm sure they'd work from those and convert them to NTSC for the increased resolution--but they're not. the NTSC masters are what they have, and the PAL DVD's will be sourced from that.