The phrase "avtal på option" doesn't translate easily and I don't actually think it's good Swedish. I propose you rewrite the sentence along these lines;
"A new enterprise agreement was optionally entered into during 2015."

You presumably have more background context here, but this sentence reads (in somewhat sloppy/shorthand Swedish) like there was a previous contract with an option for extension. This seems to refer to that option having been exercised so the contract was extended with specific terms regarding migration to using cloud services.

With this limited context that is still a guess, and I'd like to see more before rearranging things to say it better.