He can certainly use the space marine land raider to transport his Inquisitor Lord and friends, though it will take up a heavy support slot. Make sure he has his
HQ and 2 troop selections filled from the
SM codex as well. It's important to note that a
WH ordaemonhunter army cannot take a
LRC or
LRR as part of the allies system, as they're not on the list, only the 'space marine land raider' is.
If the parent list is the new space marines, he may have 1
hq, 1 elite, 2 troops, and 1 fast attack selection from the
WH codex. No heavy support, and you can only have allies from 1 other codex at a time. Beyond these rules, all units, transports, psychic powers, etc. work as written, and there's no longer any distinction between which codex the units came from. Generally speaking.
Oh, and for the record, I like the new
PotMS vs. the old one. You lose the movement (means nothing with extra armour) but your 1 gun fires at BS4, can fire on a different target and you can even fire through your own smoke launchers

(some people may contest that opinion, but most people I know play it that way.)