Notwithstanding any other provision of Nebraska law, any municipality may enter into agreements with an agency for the purchase of water, electric power and energy, energy conservation services or devices, energy sources or fuels, sewerage services, or solid waste disposal services whereby the purchasing municipality is obligated to make payments in amounts which shall be sufficient to pay all operating and maintenance expenses of the agency, to pay for costs of renewals and replacements to a project, to pay interest on and principal of, whether at maturity or upon sinking-fund redemption, any outstanding bonds or other indebtedness of the agency, and to provide, as may be required by any resolution, trust indenture, security instrument, or other agreement of the agency, for any reasonable reserves for any such expenses, costs, or debt service or for any margins or coverages over and above debt service. A purchase agreement may contain such other terms and conditions as the agency and the purchasing municipality may determine, including provisions whereby the purchasing municipality is obligated to make payments for water, electric power and energy, energy conservation services or devices, the acquisition of energy sources or fuel, sewerage service, or solid waste disposal irrespective of whether water, electric power and energy, energy conservation services or devices, energy sources or fuel, sewerage service, or solid waste disposal is provided or produced or delivered to the purchaser or whether any project contemplated by any purchase agreement is completed, operable, or operating, and notwithstanding suspension, interruption, interference, reduction, or curtailment of the output or services of such project. A purchase agreement may be for a term covering the life of a project or for any other term, or for an indefinite period. A purchase agreement may provide that if one or more of the purchasing municipalities shall default in the payment of its obligations under any purchase agreement, then some or all of the remaining municipalities which also have purchase agreements with the same agency shall be required to accept and pay for, and shall be entitled proportionately to use or otherwise dispose of, the output, devices, fuel, or services undertaken to be purchased by such defaulting municipality.