Except the law and their own wording requires opt-IN:
"...we need your permission to share this information among our affiliates, agents and parent companies (including Vodafone) and their subsidiaries."
Somewhat - to them anyway, permission is "granted" by you choosing not to opt-out. It's a crazy, muddled-up, mixed up world.
"Option"? IMO this should be illegal, but i'm sure there is some clause in the contract which allows such use.
I do like how it's illegal to sell a person video rental history, but totally fine to sell information that shows everywhere they are at anytime of the day.
When some Congressman gets busted by this we'll probably get a Mobile Privacy Act.