The new high school in Auburn IS in the state list. There is a formal project underway, with Maine Dept of Education involved. There is a formal "building committee" meeting these days. As your editor reads the state statute relative to debt amortization, any debt on the books of either city prior to the formally proposed merger date of Jan 1, 2020 would be assessed to the taxpayers in the existing City. Any contracts and liabilities in force in either city prior to Jan 1, 202o would transfer and become an obligation of the merged city. So, your editor supposes, either city could issue debt or enter into any agreement between the time of the merger vote (hopefully, Nov. 7th, 2017) and the merger date (Jan 1, 2020) and the debt would be picked up by the taxpayers of the existing city issuing debt but the agreements made with anyone, developers included, will be the responsibility of the merged city.
If the City of Auburn issues debt on the new high school prior to January 1st, 2020, and the voters of both cities approve the Consolidation Agreement, taxpayers on the Auburn side of the river will be 100% responsible for paying off that debt. If the City of Auburn waits until after January 1, 2020, and the merger is approved, then taxpayers of the entire merged city will be responsible for the new high school debt. We don't know what the amount of the debt will be, and it will have to be approved by the voters prior to issuance.
The same with the new fleet of Lewiston fire stations. If Lewiston starts building and finances the new stations prior to January 1, 2020, taxpayers on the Lewiston side of the river will be responsible for 100% of the debt. The debt is not issued until after Jan 1, 2020, then taxpayers in the Auburn side will pay (probably near half) of the debt.
So, the voters of either city, having approved the merger, could be very surprised to learn that they are "on the hook" to stand by an agreement or arrangement made by either city council in the 26 month period after the vote and before the merger.
You are entering a minefield. Step with caution...