The simple answer is No, the FCC doesn't want you opting people into any list. It's always better to let people subscribe on their own.
While you can import new contacts, maybe planning to send out an initial notification to tell people about the service and hope they want to stay subscribed. This does create an effort for them. If they don't want to be subscribed, they have to log in and unsubscribe from things we do not recommend doing this due to the FCC rulings.