The April date depends on the seasonal thaw and the availability of running water.
Eurasia said the two parties had agreed to a platinum revenue split of 65:35 in favour of the contractor, which is responsible for pit development, mining, ore trucking, washing and disintegration.
Techstroy produced 5,820 ounces of platinum in the 2018 mining season, exceeding the 3,500oz target, with its board deciding to register a new company, Uralmetmash, to focus on West Kytlim.
Executive chairman Christian Schaffalitzky said the contractor had been an effective operator last year, and was financially motivated to develop the mine in a sensible manner.
Eurasia remains responsible for concentrate upgrade, shipment of mine product and distribution of metal sales revenues.
To this end it also renegotiated a refinery contract with the Urals precious metals refinery to include an extra percent payment on London Metal Exchange platinum prices to 98% LME, from 97% last year.
Schaffalitzky said Eurasia was also looking at ways to improve metal recoveries, based on the measured efficiency of the existing process flowsheet.
Meanwhile, Eurasia is continuing to work on an enlarged exploration programme for West Kytlim, including the recently approved Flanks exploration license, to ensure adequate reserves available for future mining seasons.
It said it had started analysis work on previous mining seasons' performance and outlined a sampling programme for the 2018 season's tailings.
Eurasia's shares rose 2% on the news to 0.50p (US0.66c).