There are any number of FTP utilities you can use to accomplish this. Once you get the file onto the dev environment, decrypt it and put it into another location (by way of saying encrypt the backups before you move them between environments).

Then have a SQL Server job do a check to see if the file exists in that directory. The file check job kicks off the restore job and the restore job contains a data scrubbing step, a permissions update step, and any other steps you may need.

The best way to do this is schedule the backup sending at a certain time each day. Then give yourself some cushion (so as the backups grow the job won't fail by trying to lock onto the file while the file is locked by the decrypting / moving process). At that point, have a recurring job that checks for the file every X minutes within a Y hour timeframe. We use every 30 minutes over a 4 hour time frame. This gives the files a chance to decrypt properly.