Vattenfall said the collaboration with the US-based manufacturer has already been going on over the past 12 months.
In that time, Vattenfall has conducted an "in-depth technical due diligence" and "jointly worked on the customisation of the platform" with GE.
By taking a closer look at the 12MW turbine, and suggesting adaptations, Vattenfall can form bids in future tenders that are more accurate and aggressive.
The latest announcement suggested the collaboration will continue, but details of exactly how the relationship will work is still being worked out by the respective companies.
Vattenfall said it hopes to "define" the deals of the agreement by the summer. By the end of the year, both firms will take a "deep dive" into the developer's pipeline to identify projects where the turbine could be used.
Vattenfall has built a reputation of aggresive bidding in offshore wind auctions recently. Having won the Kriegers Flak, Horns Rev 3 and Versterhav nearshore projects — all in Denmark — with unexpectedly low bids.
It also won the Dutch zero-bid auction for the 700MW Hollandse Kust Zuid offshore wind project and has bid in the Netherland's second zero-subsidy round.
In a statement, GE said: "This is a technical validation made by Vattenfall that shows developers have interest in our technology and recognise the robustness of the design, and see the value the Haliade-X can bring to their offshore projects."
"The cooperation with GE Renewable Energy enables us to remain one step ahead in wind turbine technology developments," said Vattenfall's head of wind, Gunnar Groebler.
There are currently no firm orders for the Haliade-X, however GE claims various unnamed developers have bid for a total of 10GW of offshore capacity, globally, using the 12MW turbine.
GE said the development of the turbine was continuing on schedule, with a prototype due for installation in Rotterdam, the Netherlands, over the summer.
