It's basically that SBFakeCarrier variable (a text field). If it exists, even if it's equal to "", the normal carrier logo is not displayed. To get the logo back, the SBFakeCarrier must be deleted from com.apple.springboard.plist.
The way I usually do that is with the
plutil command (a file that can be downloaded from
here). When that is on the phone, the command
Code:
plutil -r SBFakeCarrier /var/root/Library/Preferences/com.apple.springboard.plist
really
removes the variable.
You could include plutil with the installation package and issue this command at uninstall. Of course the problem remains that you never know whether the user wanted to keep that setting - but it's more likely that they don't. If there was a way to ask during uninstallation, that would be best, but I don't know whether Installer is able to do that.