No, you can not use any other backup program to restore another proprietary backup. The temporary activation key is a good idea, although 48 hours makes sense. In most instances, you would be doing that move on a more temporary basis.
This is being done due to pirating. Take it as a somewhat good sign that AC has become so popular, it is being pirated now. Or that it is getting too expensive, lol.
Using the restore file as a way to stop pirating is not a good technique nor is it acceptable and who even knows if its legal.
But, until we find out more, what we can do is make backups in the traditional way. I have always felt and said so on here many times that the best and most reliable feature on AC is its .enc local backup process. But, that doesn't mean I don't have AC backed up in a hundred different ways. I have always encouraged everyone to consider their most important backup as an image backup of their main computer which is capable of backing up databases such as BackupAssist for server only or Macrium or others which specifically have modules that can back up SQL. This one should be disconnected daily plus rotated with another one.
While reading this thread I get the sense that some are backing up the .enc file to a computer location and/or just accepting the default. Waiting 24 hours for support (which is not acceptable) is still 100 times better than losing your data forever or hoping the $500 to $2000 (going up monthly) gets it back from ransomware.
I still wonder what would happen if EVERYONE sent their .enc files to support EVERY DAY and asked for validation or whatever they do. They would soon ask you wtf? But, what could they do? You pay for your support, they put this process in place. Until they limit the number of times you could use it, which would be another huge limiting step, upload away!
You know. Make backup after work. When finished, immediately upload to support and tell them it needs validation. They validate and download it back to you. That is now your backup for that day. Works for me. (that's the cliche -- not saying I am doing that)
