The Metropolitan Transportation Authority's tentative pact with New York City subway and bus workers has scrambled the deck for its contract showdown with Long Island Rail Road worker unions Monday, when they meet with federal mediators. But in whose favor the odds now stand is anyone's guess.

The mediators could simply stick with the deal a similar board recommended in December. It called for raises of about 17 percent over 6 years. But they should be mindful of the agreement the MTA struck Thursday with the city's Transport Workers Union for a more meager 8 percent raise over five years. With an LIRR strike looming as soon as July if no deal is reached, the stakes are high. The TWU deal hasn't been ratified by union members, but it already has created new facts that mediators shouldn't ignore.