It's not so much about how BAT has changed but the various options/parameters that have been added/changed between CUCM versions. I've used BAT exports to rebuild customer configurations or stand up new images (with a known configuration) in a lab environment and I'll give you the following feedback regarding what you want to do:
1. It can be done.
2. It takes close study / stare and compare, time, and trial/error (and repeat to clean up).
You'll essentially be doing a full export (or an export of the configurations that you want to export and are available for export) and then massaging those to match up with what an export/import from what BAT looks like in 8.5. You also have to carefully replace data such as CM server names and etc. so that the configuration parameters for the 8.5 system actually exist and can be added. In my experience, some things just dont always move over well either ... for example, gateway configurations. The import process will log all successes and failures so you'll have a place to look for what you need to resolve as you go thru the process.
With that said, I would tell you that it's probably better to build the new 8.5 out as you would a new system to a point and then import core configurations that are tedious to create manually such as partitions, CSS, route patterns, and phones. This does a couple things. First it reduces the "garbage in, garbage out" effect when upgrading - in other words, this is a great chance to clean up anything you don't like or just needs to be cleaned. Secondly, it reduces the time you have to invest into the BAT portion of the upgrade/migration. My last comment would be that, no matter how much data you attempt to export/import, it is to your advantage to try and work things out and get familiar with the process in a lab environment first. If you have a lab server at your disposal that you could load 7.x (something more recent than your current version) on then you will be able to work out a lot of this in advance. If you don't have a lab server, you could use something like VMWare Server or VMWare Workstation and go that route too. If you can't work out the "lab" testing portion then well, so be it...but I speak from experience in that it will be of great benefit to you. Lastly, whatever you do - make sure to get a DRS backup of both systems but particularly the new one. If you start importing data and run into errors then sometimes it's easier to just restore the DRS backup to a clean image, fix up the BAT files, and give it another go. You never know how handy a clean backup is until you don't have one.
That's all from me at the moment. I'll be glad to attempt to answer other specific questions you might have. Again, BAT is an option...it just takes some planning and consideration.
Hailey
Please rate helpful posts!
