Just weeks ago, a sweeping overhaul of the nation's telecommunications laws seemed a sure thing. But now the measure is on hold. The sticking point: how fast to let the seven Baby Bells into the long-distance business. A House-passed bill would let the Bells in after a fixed period of time. But long-distance companies fear the Bells would use revenues from their local monopolies to subsidize long-distance service. And they persuaded key senators to adopt amendments that would let the Bells in only after they face real competition in their local markets. As a result, the Bells have withdrawn their support for the bill. Although the White House is trying to broker a deal, with Congress expected to recess on Aug. 12, chances of legislation passing this year are dim.