Judging by the date of that article, I'm guessing the Writer's Strike later that year halted any London spinoff. Also WP left CSI the following year. Also IIRC, there was talk of William Petersen going to London for a CSI ep clear back in 2004 and 05. Possibly a pilot for a spinoff, I think. Anyway, it didn't happen because he was diagnosed with an irregular heartbeat at that time. That's why WP isn't in some episodes of season 5 much.