On 10.8.5 or earlier systems, Migration Assistant will not see the backup disk(s) created with 10.9, because it will have been created by a newer version of Time Machine and needs the newer version of Migration Assistant! Same will happen if you try to see a clone disk created with 10.9 system.
In fact it seems to me that MA of any system will not be able to see the Time machine or any clone disks created using a newer system, even if some of the backups are of the older system.
So if you are trying to revert back to 10.8.5, like I am, then your only chance to restore your 10.9 apps and settings is by manually copying files and folders, and THAT will take a long time and cumbersome detailed searches of want you need and where to find them so you can copy them.
I have been on the line with Apple Support for at least an hour and this was the result we reached.