Subways, buses, and commuter trains will operate as usual this week, but the state's embattled transit system remains in limbo, pending a ruling by Massachusett's highest court.

Gov. Edward J. King announced Saturday that a fare increase--the second in less than six months--may be necessary to improve the financial health of the ailing system.

The Supreme Court Saturday negated a lower court's ruling that King's takeover of the Massachusetts Bay Transity Authority (MBTA) was illegal, and thus averted the latest shutdown threat. The ruling would have gone into effect yesterday.

While the high court temporarily paved the way for continued mass transit service, a shutdown later this month is still possible. The key issue--whether the governor's emergency powers permit him to spend state money without a legal appropriation--remains unresolved.

If the court rules King cannot spend the $41 million needed to keep the bankrupt system running for the rest of the year, the area's 250,000 MBTA riders may find service halted immediately. "I would think that (a shutdown) would have to happen," King told a press conference Saturday.

Confident the court will uphold his takeover, King now is doing little to develop contingency plans. "We are on hold like everything else," Gerard Morris, King's press secretary, said yesterday.

King's legislative proposal for reorganization of the debt-plagued MBTA was soundly defeated last week, but King has not yet filed amended legislation. He allowed the legislature to adjourn Thursday without taking action to resolve the crisis.

King indicated he would make one more attempt to work "within the system." Wednesday, at a meeting of the MBTA Advisory Board, he is expected to renew his request for a $41 million supplemental budget to tide the system over until January.

But King's actions in the past week have further antagonized the board, which precipitated the crunch by denying the MBTA's request for more money unless the authority's management was reorganized.

Sources at the board yesterday described King's plan for second fare increase as "unnecessary" and the "wrong solution to the T's problems."

"If King thinks a fare increase is going to eliminate the deficit, he will have to raise fares to three or four dollars per ride," Thomas Ziola, the board's budget analyst, said yesterday. King justified the fare hike by saying, "I believe in the users paying... What the user does not pay is paid by the taxpayer."

Since the board attributes the MBTA's persistent financial troubles to wasteful emplyment practices, it was further infuriated when King's acting secretary of transportation, Barry M. Locke, announced that he will hire 250 new employees.

Locke dismissed the effects of tax-cutting Propositon 2 1/2 on the state's hard-pressed cities. He told the municipalities, "You can't say that because the cities and towns can't hire, we can't. We're a transit authority. The same rules that apply to communities shouldn't apply to us."

It costs the government $1 million a day to operate without a legal appropriation. Whether the state will pick up the entire tab or whether the cities will pay half is still at issue.

King's attempt to collect $6 million from cities and towns for transit expenses during his December 1979 takeover is still being contested in the Massachusetts Supreme Court.

The Advisory Board, which is worried about the impact of a rising transit deficit on local property taxes, shows no signs of yielding. So even though the T is running this week, nobody knows for sure whose money it is using.