I sent this to support and was told that Aha doesn't support it. I'm in the market for a PM tool for our company, but it needs to be able to import the (almost ) 1000 feature requests that we keep in Redmine, and the thousands of tickets that we keep in Mantis.
This can be achieved by importing redmine issues to Aha! via CSV. You can do this by going to Settings -> Product -> Import from CSV.