Hi Martin - No, this solution is NOT using Oracle's Transparent Gateway product. And I would suggest that you never use OTG! Oracle doesn't support it very well and you end up with broken data feeds because they don't keep up with the latest versions of the other databases. We've been burned enough times that we've tossed it out!
Hi Brian - Where is your Oracle database running? If it's running on a Unix machine, you need to get the Teradata tools for that OS. To be specific, we have Oracle running on Sun Solaris. We got the Teradata Utilities Foundation (TUF) for Solaris. This includes things like ODBC, JDBC, BTEQ, FastExport, FastLoad, and the lower level CLI & CLI2 to make them all work. These all get installed on Solaris. Then, define an ODBC data source that points to your Teradata Database. Then, from within the Oracle database, you create a database link that uses the ODBC data source. You can create synonyms to make the link easier to use, but that's basically it. We have it working and it works great.
The details are a bit much to post here, but basically, get the Teradata TUF for Solaris and get it installed. Then get a good Oracle DBA level book and look up creating DB links using ODBC data sources.
Hope this helps.