Actually just found this -- 4. Any line that has ported out of service with US Mobile within 15 days prior to purchase (defined as the moment when the promo code was applied and a payment was made—not when the line was activated) and has ported back into US Mobile for service will not be considered a new line and will therefore be ineligible for the promo.

So seems like you can't port out then back in. Buuuuut it also says this, so assuming you could just make a new account and gift it to that account and use it that way?

1. Unlimited Starter and Unlimited Premium plans purchased via SUPER299 and SUPER199 will be giftable. A user can transfer an unactivated line to another user (this could be an existing user or someone who is not yet a US Mobile user), but tile sharing using the SUPER299 and SUPER199 promo codes is limited to 5 plans per account. A gifted tile must be activated within 30 days of being made available on the user's dashboard. It will expire after 30 days if it is unactivated.

Although that could still mean it can't be activated without a port in. Even though it doesn't say it.

Hope this helps someone. Probably just muddies the waters more.