It is believed the deal will be formally announced tomorrow.
It is understood that Countrywide will not be buying the firm out right but entering into some form of partnership.
Countrywide has made no secret of its intention to acquire a brokerage and was rumoured to be looking at Savills Private Finance.
In April it bought mortgage network Mortgage Intelligence Holdings and last June it bought Hamptons International.
Mortgage Strategy revealed last November that it had a bid for Personal Touch Financial Services turned down in 2010.
Peter Brodnicki, chief executive of MAB, was unavailable for comment.