Okay, I’ve asked around a little and done a bit of research, and this is how the TMG Yaris R1A fits into everything:
Basically, the existing car classes – Super 2000, Group N and Group A – are going to be discontinued (though the WRC class will continue). No new cars will be homologated under these rules. Instead, the entire class system is going to be restructured with the new R-class cars. Every car that is homologated will be placed into one of five classes, designated R1 through to R5. Every car within these classes will be given a further designation referring to engine size. The Yaris is in Group R1A, which is the entry level: the cars are small, simple, and very close to their road-going counterparts.
Here are some examples that I have found:
Class R1
2WD cars with minimal modifications – very close to stock cars
R1A – 1.4-litre, naturally aspirated (ie Toyota TMG Yaris)
R1B – 1.6-litre, naturally aspirated (ie Renault Twingo R1, Ford Fiesta R1)
Class R2
Still 2WD, but with more modifications than the R1 class
R2B – 1.6-lire, naturally aspirated (ie Skoda Fabia R2, Citroen C2 R2, Peugeot 208 R2)
R2C – 2.0-litre, naturally-aspirated (no cars homologated under R2C regulations – yet)
Class R3
Top 2WD drive class, with potential for more modification than R1 and R2
R3C – 2.0-litre, naturally-aspirated (ie Renault Clio R3, Honda Civic R3)
R3D – 2.0-litre, diesel (ie Fiat Punto R3D
R3T – 1.6-litre, turbo (ie Citroen DS3 R3T, Peugeot 207 R3T)
Class R4
For existing Group A and Group N cars, with modifications
Class R5
Newly-created successor to Super 2000