Yes! It is possible to migrate ccNewsletter information (subscribers, newsletters etc) from Joomla! 1.5 to Joomla! 3.x. Also read "End of Joomla! 2.5 & how to move to Joomla! 3".

We have different migration manuals for this extension:

It is very important that you install the correct version of ccNewsletter in both sites!

Method 1: moving the database/files during migration

  • On the Joomla! 1.5 website:
    • create a backup of the Joomla! 1.5 website (with Akeeba Backup)
    • make sure you are using the latest version of Joomla! 1.5
    • make sure you are using ccNewsletter 1.3.x
    • use your favorite extension to migrate your Joomla! 1.5 website (SP Upgrade) and in that extension make sure to enable the option to also move ccNewsletter's database tables. SP Upgrade has this option, ask the extension developer if you can not find it. This will allow the extension to also "move" the ccNewsletter information to the new Joomla! 3.x website
  • On the Joomla! 3.x website:
    • after the migration it should be enough to install ccNewsletter 1.4.x, after which ccNewsletter will recognize the database tables and work again
    • do a full check of ccNewsletter to make sure everything works, for example check newsletters, subscribers, the subscription module (if used), menu items and configuration. It might be easy to just go through the ccNewsletter manual and and use that as a reference
    • it is now possible to update ccNewsletter to the latest version we have available for Joomla! 3.x

Method 2: moving the database/files after migration 

For this method, experience with PHPMyAdmin (or similar) is required 
  • On the Joomla! 1.5 website:
    • create a backup of the Joomla! 1.5 website (with Akeeba Backup)
    • make sure you are using the latest version of Joomla! 1.5
    • make sure you are using ccNewsletter 1.3.x
    • login to the MySQL database of the Joomla! 1.5 website, on most hosters you can use PHPMyAdmin to reach the database, ask your hoster for details
    • find the ccNewsletter tables, they start with #__ccnewsletter__XXXX where #_ is a random prefix and XXXX is the table name (for example: jos_ccnewsletter_subscribers)
    • select all ccNewsletter tables, and export them with PHPMyAdmin
  • On the Joomla! 3.x website:
    • login to the MySQL database of the Joomla! 3.x website
    • import the tables you just exported into PHPMyAdmin
    • after the import it should be enough to install ccNewsletter 1.4.x, after which ccNewsletter will recognize the database tables and work again
    • do a full check of ccNewsletter to make sure everything works, for example check newsletters, subscribers, the subscription module (if used), menu items and configuration. It might be easy to just go through the ccNewsletter manual and and use that as a reference
    • it is now possible to update ccNewsletter to the latest version we have available for Joomla! 3.x