During oral arguments, Justice Deno Himonas also said if the Supreme Court kept the lawsuits, a good chance existed that it would rule against the referendums on procedural grounds rather than their merits.
Himonas also said the district court would be more likely to issue an injunction to temporarily halt the project during its review.
At issue are two no-cost leases approved by city councils in Provo and Orem to allow the Utah Transit Authority to use some city streets for the project, including for dedicated bus lanes or other facilities such as bus stops.
The Utah Constitution allows citizens to collect signatures to force an election to overturn any legislative action by a city council. Citizen groups say approving the leases qualifies, and they collected enough signatures to force an election.
However, the two cities rejected the petitions, arguing the leases were administrative actions not subject to referendum.
The citizen groups contend that UTA is trying to speed the project so that so much money will have been spent on it before any election that voters would be unwilling to halt it.
The UTA Board in July approved launching the project immediately, proceeding without $23.8 million in advance funding that it says federal and county governments almost surely will reimburse later.
Last month, UTA also unveiled its proposed 2017 budget that includes $120 million for the project showing construction could be well advanced or nearly finished before any vote in November 2017.
UTA describes BRT as "TRAX on rubber wheels," where passengers must buy tickets in advance. Extra-long buses would have bus-only lanes for about half their 10.5-mile route, and may receive priority at traffic signals. They would come about every six minutes at peak times. The route would include Utah Valley University, University Mall, Brigham Young University, downtown Provo and the Provo Towne Centre mall.
Opponents say the project is too expensive, will not be well used and will constrict other traffic. Officials say it will reduce congestion and air pollution.