If he is being assessed under the new rules, his new wifes earnings are not taken into consideration.
Actually, this is can apply to old rules as well as the CSA insist they only take the new partners earnings/income into consideration to make sure the one who pays CSA can manage to do so. I find this rather dubious.
My husband is assessed under old rules and maintenance I receive for my two eldest children is in the assessment ~ I don't think this is right, but there you go! I worked too, just to make sure we had enough money to live on.
Personally I think that only the 'absent parent' should be assessed, as it's their child who maintenance is paid for.