I've had a second ATA, same credentials on my two line phone.

I don't think 2-line will be a likely thing because the average user will not have access to their setup details.

If VOIPo had handed out GS with two phone ports, it could have been a cool promotion, and maybe only for users that have been with them long enough? Say 2nd phone port after 4 months with VOIPo as a retention thing.

Whatever they do with soft phone might be a more likely 2nd line possibility. Especially if the softphone is just a second instance of the primary line. Perhaps tied to a MAC ID?