TrueCrypt requires an "environment" to run, whether that be Windows, Linux, Or Mac OS. This would not be possible because there is no DOS version of truecrypt. Therefore, neither with YUMI nor UBCD would you be able to decrypt a partition/file. Your best bet would either be use a Linux LiveCD/DVD with TrueCrypt included and run the programs you need after decrypting the drive, or building a WindowPE, good guide is here: https://gverswijvel.wordpress.com/tag/winpe-5-0/
Sorry to disappoint.
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Please check your UBCD
ISO MD5 Hash Sum
; May prevent issues later on by not having an exact copy.
Currently Working on Common Issues and Repair Tips
on the Wiki.