In Virtualbox, if you use the export option “include MAC addresses of ALL network adapters”, you can use the exported image as a full backup of your freePBX system.
If your hardware fails, you can import this image into any VirtualBox installation on a Windows, MacOS or Linux machine and it will behave like the original (same ID, no activation needed).
The critical point seems to be that you have to copy BOTH MAC addresses, WIFI and ethernet. The harddisk and other hw parts are virtualized (and therefore identical) anyway. But I may be wrong 