In a move that left many analysts puzzled, CBS announced on Monday that it had taken a stake in Syncbak, a company that allows broadcasters to stream their programs to mobile devices over the Internet -- just like Aereo, a company that CBS and other broadcasters are suing. The technology behind Syncbak presumably is different from Aereo's -- which employs tiny antennas, each one assigned to a different subscriber, to pick up broadcast signals. But the effect is the same. In a statement, CBS exec Martin Franks described Syncbak as a very elegant technology platform, which presents several interesting opportunities for broadcast networks, their stations and affiliates. A news release said that The National Association of Broadcasters and the Consumer Electronics Association were also among Syncbak's investors. The amount of the investments was not disclosed. It was not clear just how CBS or other broadcasters might employ the system. Some analysts suggested they might use it as a TV everywhere service to cable subscribers -- but nearly all cable companies already offer such a service. Other analysts speculated that it could be offered as a stand-alone service, like Aereo. If so, why then, they asked, didn't CBS simply offer to buy a stake in Aereo instead of mounting an expensive and dubious legal battle to put them out of business? Meanwhile, Aereo announced today (Tuesday) that it will expand to Boston on May 15. It currently operates only in New York City.