News of the ad policy change comes as new figures show the T has spent at least $560,000 thus far to fight a 11/2-year-old federal lawsuit over efforts to place pro-marijuana ads on MBTA trains and buses, a cost expected to rise as T management vows to fight on despite planned policy changes.

The MBTA's new ad policy, which may go before the T board for a vote next week, is written to provide a clearer, ''more objective'' review process for ads as well as more legal review.

Currently, the T has no written standards to provide advertisers for assessing their ads. The agency's marketing department reviews ads and recommends whether they be allowed or challenged if they are deemed obscene, violent, harmful to children, or denigrate groups based on gender, religion, race or political affiliation. Traditionally, the MBTA has taken a conservative stance on questionable ads.

Mulhern said he will now become involved in the review process. The new policy, which is in the final draft stage, will provide written criteria that will be disseminated.

Under the proposed policy change, Mulhern said that many ads rejected in the past by the T would be allowed to run, including a recently banned church ad that criticized the commercialization of Christmas.

But Mulhern said he has no intention to relent on the T's effort to keep out ads he says promote the use of illegal drugs that Change the Climate, a Greenfield-based group, is seeking to place in buses and subway cars. The group, which is represented by attorney Sarah Wunsch of the American Civil Liberties Union of Massachusetts, filed suit in US District Court almost two years ago.

Change the Climate provided the Globe with the T's legal costs after obtaining billing documents under the Freedom of Information Act.

The group and Wunsch estimate the T's total costs thus far at $561,000. T spokesman Joe Pesaturo said the $561,000 includes both the cost of defending the agency and of paying the Boston law firm Hill & Barlow to help create the T's new ad policy.

The latest fight with Change the Climate is the T's fifth legal battle with a would-be advertiser in three decades, but the first to go to trial. The judge hearing the case has yet to render a ruling.

Wunsch alleges that the tough stance taken by the T was heightened in the fall of 2000 when then-governor Paul Cellucci vowed never to allow the ads.

The funds spent trying to bar ads from the T have not produced any victories; the agency has lost every legal battle.

Among the fights was a case involving ads for the AIDS Action Committee, which reached the First Circuit Court of Appeals. In that case, the court ruled that the T's ad policy violated the First Amendment because it was vague and lacking in adequate standards.

Despite the ruling, Wunsch said the T did not review its policy, which makes her skeptical that the T will dramatically alter its policy now.

''Why didn't they do it then?'' she asked. ''I'm reserving judgment on what they're saying now because we've seen many different versions of their advertising policy.''