ATU President Antonette Bryant said the unions were anxious to see the offer. She reiterated that the unions do not want to strike.
If the clock strikes midnight with no agreement, workers could walk off the job, stranding an estimated 400,000 rail commuters. Last July, BART workers struck for 4 1/2 days, leading to jammed bridges and roadways, and crowded buses throughout the Bay Area before Gov. Jerry Brown mandated the cooling-off period.
On Wednesday, union leaders thought they had a deal with BART management but said the proposal presented late Tuesday was rescinded.
"We thought we were really close and they totally yanked it off the table," Bryant said. "We gave them a counteroffer, and the next day they said, 'Oh, you misunderstood what we proposed.' We said, 'No we didn't.'"
Hock said BART never made a formal offer and blamed a mediator for the confusion.