The group has bought the 85-strong agency through a five-year earn-out involving an undisclosed downpayment to founders Nick Band and Gill Brown.
Subsequent payments will be performance-related.
Although the deal’s overall price tag has not been disclosed, B&B had fee income of just over £4.7m in the latest PRWeek Top 150 (PRWeek, 23 April).
Around nine other staff will also benefit from the acquisition, including CEO Gerry Hopkinson.
Prior to the acquisition, around 20 per cent of equity was held by staff, with B&B’s founders and senior management holding the rest.
Band told PRWeek that although the firm would maintain its independence for the duration of the earn-out, he expected B&B to pitch jointly for some business with London brand consultancy Identica, which Cossette acquired last year.
Cossette’s acquisition of B&B is part of the group’s expansion into Europe. The group’s main PR subsidiary is the Canadian firm Optimum Public Relations.