alternatively you can download the pre-patched premium voices from this thread
http://www.navitotal.com/forums/showthread.php?3263-iPhone-4-Device-ID&p=19984#post19984then you just need to install into your TomTom App folder /voices on the device with winSCP
(you would require OpseSSH installed)
or you could add then into your ipa file and sync
the IPA file is actually just a Zip archive file
1) rename the .IPA to .ZIP
2) unpack the zip
3) add your voices to the voices folder
4) repackage the files to a new ZIP archive
5) rename the new ZIP to IPA
6) add the new custom IPA to iTunes and sync