Subscribers have nothing to do with the theme if you are thinking it did.
You can export your subscribers by going to blog stats and in the "general" section click on subscriptions, then click the X active" next to "Site:" and you can download a CSV file. Unfortunately I've not found any email subscription services that allow you to import them (probably a hedge against spammers).
The built-in email subscription thing here is a wordpress.COM feature. It is not built into the core wordpress software, so no direct way of doing it.
I use feedburner's subscription service, but there is no import.
Likely all your subscribers are going to have to "re-up" at your new site.