AT&T has raised the idea with T-Mobile's parent Deutsche Telekom of a network joint venture if the now doubtful T-Mobile merger isn't approved, insiders divulged Wednesday. The two are purportedly in early talks that the Wall Street Journal understood would see them share parts of each other's network, even as they ran separate competitive businesses. The deal is considered a "back burner" option but was gaining momentum as resistance grew to the merger.