Cars that are listed in the "Touring car" class
--Premium--
IS F Racing Concept '08
(Seriously? only 1?)
--Standard--
Audi:-------------R8 LMS Race Car '09
Mercedes-Benz:--CLK Touring Car '00
Audi:-------------R8 LMS Race Car (Team Playstation) '09
Opel:-------------Astra Touring Car (Opel Team Phoenix) '00
Audi:-------------Abt Audi TT-R Touring Car '02
Opel:------------ Astra Super Touring Car '02
Audi:-------------A4 Touring Car '04
Alfa Romeo:------155 2.5 V6 Ti '93
Vauxhall:---------Calibra Super Touring Car '94
Opel:-------------Calibra Touring Car '94
Mercedes-Benz:--190 E 2.5-16 Evolution II Touring Car '92
These are all "DTM" Touring cars. (Not including the R8s for obvious reasons)
Source: I have every car in the game except special edition content (and a few stragglers like the 2J), so I just used the online lobby restrictions.
@iainoflo85
The FTO was dreamed up by Polyphony if I remember right to meet touring car specs
The Touring Car Park is simply a set of "Race Modified" cars as Furin said, not technically "Touring Cars" despite the name given to them by Polyphony Digital.
Other than that, the cars you've listed seem to be just general "Touring cars"
As far as my research has brought up these cars have competed in many different racing series but no single series in particular unlike the DTM category.
But it's beside the point, the cars listed in my post are the cars allowed by the "Touring car" filter which was the OPs question