Ah, I'm sorry I didn't make myself clear. I was not wondering if there was a way to combine the templates. I was thinking that a story where a wizard sought out an apotheosis of sorts, very much like House/Clan Tremere in oWoD. So I understand that it would be easier metagame-wise to start off as a WCV and then move to learn magic, but that wasn't the intent behind the question.
No need to worry - you were perfectly clear. I don't think we were giving a metagame answer or taking templates into account. Templates are easy - if you have the Refresh to take both, you can take both.
The issue is that the source fiction exclusively describes WCV as reproducing by bloodline, so you are going to see that most Dresden fans are going to balk at the idea of someone becoming a WCV by any other means (like this Tremere Apotheosis you mention). Dresden Files is a different setting than World of Darkness, and if there was a way to *make* someone a White Court Vampire, then that might have been discussed between Thomas and Justine at least once in the writing as a bittersweet solution to their awkward relationship, but it is never proposed.
That said, a GM could certainly write their story to make it possible. One could establish that the WCV Houses were, at one point in the distant past, pure mortals, and explain that they made pacts with a particular type of Demon, a genetic pact which would pass down through their bloodlines and ensure that this Hunger Demon would multiply in power through its children. If a GM set this up as a setting feature, then I can imagine it would be more plausible to seek out the attention of this Hunger Demon and try to start up a new bloodline.
But that would be a special thing which a GM sets up for their version of the Dresdenverse. But if we are sticking to the setting as written, then it is going to be near impossible to make someone WCV. And we all know that the Impossible is made Possible through Thaumaturgy. Which would probably accomplish the same effect as this Tremere Apotheosis.