Hmm, interestingly my com.apple.MobileInternetSharing.plist keeps reverting back to.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>State</key>
<integer>1021</integer>
<key>Version</key>
<integer>2</integer>
</dict>
</plist>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>State</key>
<integer>1021</integer>
<key>Version</key>
<integer>2</integer>
</dict>
</plist>