Will the TTL sockets work with the Phicen feet?
Yes. I just popped a pair of Phicen loose feet into a TTL base female body with no problem. As EMHall said, most ball joint ankle pegs are completely interchangeable in base female bodies. I've mixed and matched loose feet from Triad, TTL, ZC, and BBi/Takara, and it looks like the new Flirty Girl and Verycool base bodies are still keeping the compatible ankle socket.
FWIW, the double-ball ankle pegs that came with Toys City/TTL MALE bodies will also fit in those ankle sockets. ZC did a set of molded Converse sneakers but didn't include ankle pegs, but grabbing some male TTL ankle pegs worked well (though they did make the figure noticeably taller). I think the new DAM Toys ankle pegs are compatible as well, but I haven't tried.