This conversion seems like an attempt to convert TurboTax tax return files. You cannot just simply convert tax return files from one year to another, so this conversion does not seem likely. At best you can import and review some data from the tax return files, but thats it.
Convert TurboTax Canada 2011 tax return to TurboTax 2012 tax return file.
We found 2 software records in the database related to .tt11 to .tt12 file format conversion.
Microsoft Windows software - convert tt11 to tt12 on Windows
A tax preparation software developed by Intuit
Convert from tt11 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned tt11 to tt12. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert tt11 to tt12 on OS X
Popular tax preparation software