Today I found a good project's report of a guy's final studying project which is to
"build an HbbTV application over a DVB-S signal during the FIFA 2010 World Cup event".
Here is the documentation (67 pages).
He is also using OpenCaster and free tools like DVBsnoop under Linux.
You can see how he managed to fill the DVB SI tables to handle an HbbTV application.
But now this is integrated inside OpenCaster so you just have to use them without worry.
Nevertheless enjoys this good experimentation.