BlackBerry maker Research In Motion has hired law firm Milbank, Tweed, Hadley & McCloy LLP to work out a restructuring plan that could include selling assets, seeking joint ventures or licensing patents, people briefed on the matter said.

As part of the struggling Canadian smartphone maker’s strategic review, the RIM board is discussing ways to boost revenue from its new BlackBerry 10 operating system and possibly opening up its proprietary network, the sources said.

At one point, RIM was hoping to add as much as $4 billion in revenue from deals with major telecom carriers, sources said.

“This is a very mature strategy and RIM was very far down the road with a lot of those discussions with carriers,” one of the sources added.

The restructuring efforts come as the Blackberry maker tries to stem customer losses to Apple Inc’s iPhone and smartphones running Google Inc’s Android software.

RIM posted a $125 million loss in its most recent quarter as it wrote down BlackBerry inventories. It took an even larger hit on its underperforming PlayBook tablet computers three months earlier. RIM’s stock has plunged 75 percent in the last 12 months, giving the company a market value under $7 billion.