Sporveien has, until 1.6.2018 carried out the work of replacing hoops on tram type SL79 itself, whilst maintenance and repairs of wheel bosses have been carried out by an external supplier. Due to the start-up of alterations to the Grefsen base on 1.6.2018, Sporveien has temporarily outsourced the work of replacing hoops whilst this competition is completed. Sporveien would now like to outsource the entire process, including maintenance and repairs of wheel bosses, to one and the same supplier until tram type SL79 is phased out and replaced by new tram deliveries. A new supplier of new trams will be chosen in June 2018.