This is a confirmation of earlier news/rumors about Captain Jack returning to Doctor Who's series 3. The complete article is from SyFyPortal and contains some slightly spoilerish info on Torchwood. Enjoy!
http://www.syfyportal.com/news.php?id=3008 “I will be in [season] three of ‘Doctor Who,’” John Barrowman said excitedly. “I will be in the last three episodes of four episodes, and the scripts are being written as we speak because I just got a text from Russell [T. Davies] telling me that he’s finishing the script that Jack returns to ‘Doctor Who.’”
Although Jack will be stepping back into the mother series, it doesn’t mean there is a crossover episode on the way … and Barrowman said he himself is quite happy to keep the two shows, "Torchwood" and "Doctor Who," apart.
“You will never see, you will never have ‘Who’ crossing over into ‘Torchwood,’” Barrowman exclaimed. “‘Doctor Who’ is for children, is a base for family viewing and children. ‘Torchwood’ is not. The only person that will cross at this point will be Jack going back and forth…’’