The legal fight between AT&T and the city of Atlanta over millions of dollars in utility-relocation costs has taken a new turn, manifesting in a bill under consideration by lawmakers that affects the Atlanta Beltline.

Senate Bill 4, sponsored by Sen. Steve Gooch, R-Dahlonega, effectively paves the way for the Beltline to pursue a public private partnership to help fund a planned light-rail system.

But in recent weeks, lobbyists for AT&T successfully tacked on an amendment to the bill that would require Atlanta, which oversees the Beltline, to pay for any utility relocation costs associated with the transit effort. City leaders say that’s not only financially unfeasible, but a violation of long-standing agreements that require utilities to move equipment for major infrastructure projects.

The battle over SB 4 worsens already tense relations between the city and AT&T, which filed a lawsuit in January seeking to recoup money the utility company spent moving lines to make way for the Atlanta Streetcar. AT&T believes the city should reimburse $5.8 million. City officials disagree.

Mayor Kasim Reed said that the amendment equals death to the bill. The consequence, Reed continued, is that the Beltline’s plans for transit expansion will be further delayed.

Reed has eyed public private partnerships as a way to finance the future light-rail system that, according to 2013 estimates, could cost about $2.3 billion and would connect with the existing Atlanta Streetcar.

“The bill that we’re advancing allows us to move Beltline projects faster, because it allows third party investors to pay for parts of projects,” he said. The amendment “puts the bill in jeopardy, unfortunately, after we put in a great deal of work. It would damage the Beltline.”

This is the second year Atlanta has lobbied for the effort, after a similar bill failed last year on the final day.

In the current dispute, utility companies argue that the Beltline’s planned transit component is about economic development, not transportation as SB 4 states, and therefore ratepayers shouldn’t be on the hook to fund it.

“Those that benefit from the project should bear the cost of the project,” said AT&T spokeswoman Stephanie Smith. “We do not believe our customers throughout the state of Georgia should bear the cost of these projects.”

Beltline backers say AT&T is attempting to use the bill to settle and ward off future payment disputes. SB 4 has no bearing, however, on the existing lawsuit.

Lobbyists for Comcast have joined in the fight, testifying in favor of the amendment in recent weeks.

SB 4 reached an impasse between the House and Senate and is now being hashed out in conference committee — a group of six legislators from both chambers who must try to reach a compromise by Thursday’s end. The committee met Wednesday, but failed to find resolution.

They’re set to reconvene Thursday morning, where they could decide which version of the bill — with or without the amendment — will move forward. Gooch could also pull the measure, leaving the Beltline to try again next year.