Does the importer map their existing IPs?
It uses the default IP address configured for the v3 server.
It is NOT importing their existing Port Numbers. It is assigning them new ones based on the range specified in the setup of CCv3.
Is this possible to get working?
Hmmm, that's actually a very good point. What we'll have to do is set it up so that it uses the originally-configured port IF it's available, and auto-allocates a new one if not. The reason for this is because it's possible to import multiple v2 installation into a single v3 installation (or to import v2 accounts into a v3 installation that already contains accounts), so there may be port conflicts... I hadn't even noticed/considered that it reallocated them though, and clearly we do want at least a best effort.
Working on that now, back in a bit...