I am using Trac 0.11.7 from lenny-backports on a Debian Linux w/ Apache.
I just tried to install the pre-compiled egg and a custom cooked one from the 0.5 version, but it wouldn't start working. Trac was logging to the DEBUG log that it got installed correctly, after I uploaded it via Web Admin UI.
But I received no error what so ever, not even with logging set to DEBUG!
It just wouldn't work.
I removed the -trac0.11 suffix from the version number, cooked and installed - and it's working!
Had the same issue with another plugin today that was tagged as dev and with the revision number, so sth like "0.3dev_rev1234" and it wouldn't work. Removing all that stuff made the plugin work...
What kind of bug is that? I tend to believe it's with Trac and not with BatchModifyPlugin, but as you started using the version suffix, some other people might run into this issue, too...