Can the event Infamous! be used to steal the power that might be given out as a result of the prized Keyword?

Yup. Prized power is claimed for your house so Infamous should be able to steal it.

Agree the answer is probably yes, but until we see the actual rules insert for prized, we can't be sure.

The Quill & Tankard guys seem to have scanned one. You can find it here: http://www.cardgamedb.com/index.php/index.html/_/game-of-thrones/quill-tankard-regulars-issue-33-r962. The wording is "claims X power for his or her House".