There might not have been one singular take-away line from Wednesday night’s mayoral debate a la the “Dan Inouye is out of touch” doozy that carried the Honolulu news cycle for days after the first time Ben Cayetano, Kirk Caldwell and Peter Carlisle got together.

But tonight’s sparring — the first of the year to be broadcast live on television — had as much or more punching and counterpunching.

Infrastructure, like sewers and potholes, came up again and again. There were questions about ethics and leadership style, fireworks and prostitution, trash and homelessness.

Rail was still a central topic of debate, with Carlisle and Caldwell fighting over who should take credit for progress on the project and Cayetano continuing his push to kill the system. Caldwell called Cayetano’s bus transit plan a “disaster.”

One of the exchanges that foreshadows a key subject for the final 10 weeks before the Aug. 11 primary election focused on the Bus Rapid Transit plan Cayetano has floated as a transit alternative to rail. Pressed by Hawaii News Now reporter Keoki Kerr for specifics — How will it be better? How much will it cost and how will we pay for it? What routes will it take? — Cayetano largely demurred and shared few new details.

He said his plan is based on a 2003 study by Parsons Brinckerhoff that rated BRT superior to rail, and that he expects it will cost less than the $1 billion the contractor estimated a decade ago. Cayetano said the first phase would include synchronization and more express buses, and the second phase would include dedicated lanes.

Caldwell in particular jumped all over the plan a day after a new study showed Honolulu’s traffic is the worst in the nation.

“We’ve heard it may be elevated with massive off-ramps and on-ramps coming into our town,” Caldwell said. “Most congested city in the entire country, and Ben wants to dump hundreds of more buses onto these roads, adding to that congestion. That’s not a plan, that’s a disaster.”

Carlisle too wanted more details.

“What are the specifics? And we’re not getting the specifics. What roads are going to be taken down. What different lanes you’re going to be, how they’re going to be separated from the thing? Are we taking up the shoulder roads? I heard something like that,” he said. “Those are the details people want to know about.”

Cayetano scored some points of his own.

He asked Caldwell how much it would cost to extend the rail system from Ala Moana Shopping Center to the University of Hawaii at Manoa. When the former acting mayor dodged, Cayetano showed he did his homework, citing a recent memo from the Honolulu Authority for Rapid Transportation to the Honolulu City Council estimating the total cost for a system going to both Waikiki and Manoa (as well as the minimum operable segment between East Kapolei and Ala Moana) at $9.03 billion.

Cayetano also turned the tables on Carlisle after the current mayor posed a question to the former governor about an adviser who played a role in the 50-million-gallon sewage spill in the Ala Wai canal. What does his presence in your campaign say about your commitment to solving our infrastructure issues, Carlisle asked.

“He’s not running for mayor, I am,” Cayetano said twice. “I’d like to know what you’ve done since then because you had a heads up on the Waikiki spill and yet in Pearl City we can’t develop now because your administration called for a moratorium on development. You can’t build new homes, you can’t build a new building, you can’t build an addition to your existing home if you want to have your kids live with you, for example. That will be the case for five years, and yet you folks had ample notice on this. Nobody moved and we have this situation before us today.”

Caldwell and Carlisle, though they’re roughly aligned on rail, did manage to trade barbs on the race’s biggest single issue. They disagreed about who should get credit for the progress and rehashed an old argument about whether the February 2011 ceremonial groundbreaking for the system was phony or real.

They also sparred about the proposed merger of the Honolulu Fire Department and emergency medical operations (Caldwell says it would save money and lives, while Carlisle isn’t so sure); management style (Carlisle, accused of leaving Cabinet meetings early, said he doesn’t micromanage); and cleaning up trash (Caldwell said it was insulting to refer to the Leeward Oahu homeless camp as tons of garbage).

As the debate wound down, Cayetano noted that he considers Carlisle and Caldwell to be his friends, but he differs with them on how to run the city. The differences are likely to survive the campaign, even multiply. Will the friendships still be standing after more debates like this one?

The three candidates gather again Friday morning for a breakfast forum hosted by a commercial real estate trade organization.