To make it short, I doubt that there is very much beyond Hermetic Magic Theory, Parma Magica, Latin and Reading/Writing (Artes Liberales 1) that every Magus knows about. My impression of the order in general is that its members are pretty much self-centred, up to a unpleasant level of arrogance. Basically, many young magi will be sure that any magical deed worth their time can be acchieved by hermetic magic and that everything else (at least as far as humans are concerned) is far below their dignity.
As far as the RAW are concerned this seems to be canon, for example only one of the Magus-templates in the Core Rules has a Magic Lore score, and I am pretty sure that there is a comment in one of the supplements (can't remember which) that Magical Lore is surprisingly rare among the magi.
Actually, as a SG I like this situation, especially if I have players who don't know all the rules by heart, because this gives another opportunity for interesting twists in the story - just one example from my P&P saga:
All magi know that using vis connected with the infernal might be risky, but without an appropriate Lore (in this case infernal) they don't really know what the risks are and which kind's of vis might be more or less dangerous. Actually they stormed a medium level infernal region, which had been the hideout of a renounced corrupted magus - who actually was long deceased when they arrived. They were attacked by a bunch of corrupted animals and slew them, just to discover a ruined castle with a laboratory, some vis-laden gems, some pawns Rego-vis included in a kind of dust and jars of Vim-vis extracted in an obviously hermetic style. Bringing the booty home they had to decide what to do with the vis. Well, the stuff they found in the obviously corrupted creatures they burned on the spot, but for the rest they figured that the gems and the dust were just ordinary vis stolen by the evil magus and that vis distilled hermetically was obviously safe, too. (Reality: The Rego-dust is from a strong demon and is Vis Prava - the really dangerous stuff - as ist the Vim Vis which was distilled in the Infernal aura, the other stuff including the remains of the poor beasts was just slightly tainted - Vis Infesta.) The players got enough general warning, but their characters don't have the skills to be sure and for some reasons beyond my ability to grasp also don't check in their library, which is really well stocked in this area. Well, I can lean back and prepare a little surprise for the covenant's winter solistice-party when they cast their aegis as a Wizard's Communion Ritual and get a automatic roll of zero and about 17 botch dice. THey will have to pay a price for greed, laziness and hybris - and there will quite likely be an intereting group twilight story ahead.
So, my position: All hermetic magi have a clear idea about the stuff possible with vanilla hermetic magic, for everything beyond they will need appropriate Mystery Cult Lores or Realm Lores. Otherwise I wouldn't give more than slight hints.
Alexios ex Miscellanea