Some union workers had come back on Saturday afternoon after striking members of the United Transportation Union, which represents trainmen and conductors, ratified a new contract by a vote of 268 to 158. Members of the Conrail North division were joined in the voting by almost 100 members of the other division, Conrail East, of which Mr. Jones is general chairman. Strike Began March 1

The vote, held in the Stadium Club of Giants Stadium in East Rutherford, N.J., ended a strike that began March 1. A tentative contract was reached on Thursday, after representatives of the Conrail East division walked out of talks. Charles Serraino, one of the mediators in the dispute, said he had arranged a meeting for tomorrow morning in Newark between Conrail East union leaders and N.J. Transit officials.

Because of changes in work rules and in the basis of pay, the average salary for conductors and trainmen under the new contract will drop by about $5,000 from what these workers earned when the lines were owned by Conrail. N.J. Transit, the state's mass-transit agency, took over the lines Jan. 1.

Under the new contract, conductors will be paid an average of $31,000 and trainmen $28,000. Under Conrail's management, the average salaries had been $36,000 and $34,000. Union Leader 'Not Elated'

The general chairman of the Conrail North division, Lloyd W. Swert, acknowledged Saturday that he was ''not elated with this contract.''

Nevertheless, he said yesterday: ''I think the democratic process has spoken. As far as I'm concerned, that should end the matter and the trains should roll tomorrow.''

Meanwhile, the mediator in the strike by the U.T.U. against the Metro-North Commuter Railroad said yesterday that he had summoned both sides to a meeting at 10 A.M. today at the Metropolitan Transportation Authority offices in mid-Manhattan.