Almost a year after U.S. regulators effectively scuttled AT&T’s $39 billion acquisition of T-Mobile USA from Deutsche Telekom, the German telecommunications giant has agreed to acquire MetroPCS Communications and merge it with T-Mobile in a deal that will create the nation’s fourth-largest wireless carrier.

At least nine law firms, several of them veterans of the AT&T/T-Mobile antitrust fight, are advising on the complex $1.5 billion cash, stock, and debt restructuring deal aimed at creating a combined company that would trail wireless market leaders AT&T and Verizon Wireless, but challenge the nation’s third-largest carrier, SprintNextel.