AFAIK, random enchantments are correctly handled if the link is correctly forwarded to the API. The "+<n> Spellpower" string fragment is correctly handled in gems, and so should correctly work also in other places.
That item, before the enchant, has the spellpower. At any rate, that particular item (and those like it) are correctly detected.
What is not detected is items which have, for example, white text saying "+88 spell power" instead of green text saying "Equip: Increases spell power by 88."
Now where have I see this before ?
Ah yes, Blizzard has the nasty habit of passing color codes (among other things such as line breaks "\n" etc), inside tooltip lines :p. So you may want to make sure that, that "white" text of "+88 spell power" isn't actually "|cffffffff+88 spell power", at which point you need the parser to remove the color code, if you want to do reliable matching.
Apparently my AddOn isn't retaining a complete item link at times. I found another item which wasn't showing bonuses, http://www.wowhead.com/?item=25064, but then noticed that it wasn't showing the random enchantment. Gah.