MCA TV and Lifetime cable network are working on an unprecedented deal that would funnel an off-network series, “Northern Exposure,” to syndication and cable at the same time.Although the parties to the negotiations declined to comment, sources say that if the deal goes through, the ad-supported cable web would start stripping reruns of “Exposure” in fall 1994. But the deal would not be exclusive–MCA’s salespeople also would try to line up TV stations throughout the country to play off the same rerun episodes on Saturdays and Sundays, beginning in September 1994. No cash would change hands in the TV-station deals. Instead, MCA would hold back six minutes in each run for sale to national-barter advertisers. But, in a further break with precedent, Lifetime — not MCA — would sell the national-barter spots in the syndie runs of “Exposure.” Lifetime would be able to package the spots on the cable network’s “Exposure” run with those of the syndicated run. In exchange for getting the right to sell the syndicated barter spots, Lifetime would have to put up a dollar guarantee, which MCA would tack on to the license fee. One source says MCA started off the “Exposure” negotiations with an asking price of $ 500,000 an hour. That pricetag has come down to a figure in the $ 300,000-an-episode range, which would still make it the most expensive series in Lifetime’s history, exceeding the $ 280,000 or so Lifetime ponied up to Twentieth Television for reruns of “L.A. Law.” Jack Fentress, VP of programming for rep firm Petry National, says MCA’s strategy is a “mistake” because stations would be eager to buy “Exposure” in an exclusive syndication window of anywhere from one to four years. But other observers say there will be such a glut of syndicated product available in the fall of 1994, both firstrun and off-network, that poor demand would drive down the price of “Exposure.” An added factor is that union residuals in syndication for the actors, directors and writers add up to at least $ 100,000 an episode. For cable, the residuals would come to less than $ 40,000 an episode, depending on the final license fee that Lifetime agrees to shell out. Before a Lifetime-cum-syndication deal could come to fruition, sources say MCA would have to get the unions to agree to a drastic lowering of its syndie residuals on the basis of the limited weekend play “Exposure” will be getting on TV stations.