Fine to ask.
If your friend has CA ID, he can PPT the guns to you, and you are correct, 1-in-30 does not apply to PPT.
He doesn't even have to file paper with the state before he could sell it - the only thing that even seems to apply (CA gun law doesn't understand dual residency) would be the New Resident registration, and law says one can sell such a newly imported gun at a CA FFL instead of filing the paper.
10-round mags. He could also take the 15s apart and sell them to you as parts kits, but you could not legally reassemble them in CA.
PPT is $35, by law, for the first handgun, $31 each for any others in the same transaction. See DOJ Dealer FAQ.
Caution: There would be some question of whether he was the actual purchaser when he bought in UT. If he would really buy them for himself and decide he didn't like them, or you would enjoy them more, he could resell them. But if he were to buy them with YOUR money, or with the understanding that he would be reimbursed, rather than buying for himself he would be buying as your agent - and the only way he could do that in UT would be to lie on the 4473 where it asks if he were the actual purchaser. That's a felony; that would be bad.