In my system (and world), there's no correlation between spell lists and magical realms. So, on one side, you have open, closed and base spell lists, and, independently, one the other side, you have magical realms.
Spell lists are merely sets of spells learnt "together" the one after the other as they follow the same philosophy, whereas magical realms determine how to get the magical energy (the "fuel", if you want) to be able to cast spells. As such, I have rules governing acquisition and casting of spells (which are pretty much, as far as RM2 is concerned, the RM2 RAW, except for no differentiation between realms as all open, closed and base are considered of the caster's "own" realm), and rules governing acquisition and powering spells (which is completely different from RM2's logic, and goes very beyond the mere acquisition of PPs). so that casters from different realms aren't different by the spells they're able to cast (which is the RM way), but by the way their magical energy (thus power) varies. For instance, an Essence spellcaster draws his power from life around him so he's all the more powerful (PP and level wise) the more life abounds around him (in a huge city or forest for instance), and all the weaker the less life there is around him (e.g., in a desert), being at his lowest power level when surrounded by undead. OTOH, the more fanatical a Channeling spellcaster (I call that a "Divine" spellcaster but...), the more powerful he grows, the less devoted, the less powerful. As for Mentalism users ("Personal Magic users"), they all have a "Motivation" (a reason to live and act, if you want), and the more they act for this "Motivation", the more powerful they are (e.g., if someone has "curiosity" as his "Motivation", the more something makes him curious, the more powerful he'd get, but make him do something he thinks as uninteresting, and he'd be at his lowest power level; similarly for someone whose "Motivation" is his "friends" for instance, who get powered up when protecting his friends but powered down when fighting with enemies temporarily turned allies). Not to mention "special" abilities coming as a consequence of such a logic, such as Essence users being better at healing, Divine users being able to call for "miracles" or Personal users being able of feats of willpower. Blahblahblah, TMI already so I'll stop there.
So, to answer your question, spell lists from worshippers from different gods may overlap, first because they're merely from the same pantheon, thus have some common basic abilities, or because they have common needs. For instance, everyone needs healing, so it makes sense to each and any god to have a few priests knowing at least basic healing.
That being said, as no spell lists is tied to a specific realm, it implies no RM "profession" is either, so a priest (the actual job) may be a Magician (the RM profession) of the Mentalism realm.