Silvery - 8:03 pm on Sep 7, 2010 (gmt 0)
Your client is not an "authorized representative", so they absolutely shouldn't claim listings as their own.
HOWEVER, there are quite a lot of business directory sites which are data partners with Google, and Google Maps will take their feeds to enhance the listing data.
You should consider contacting Google Business Development for the Maps product, and see if they'd be interested in taking your feed of listings information. In return, you might get links back from Google Place pages which sport the data.