Here's a nice explanation of how it works:

Dommy says:
A small clarification: there are 2 ways you can access TMU cars, in 2 forms:

1st form - archetype
Archetypes are direct models of the cars, like already existing 4 cars. This is also default way of forcing a car on map. However, TMU cars have ValleyCar shape and CanyonCar sounds. It's the only con of this form.

2nd form - custom item
You can also create a custom item based on the archetype, as well as force 3D skin with sounds to make it feel better. These items will appear when changing model. However, it has a few major flaws:
- All players are required to have the custom item and 3D skin installed alongside the map (eg. via title pack).
- One skin is forced for everyone.
- Instead of saving the map with eg. "SnowCar" model, you save it with "Items\CustomCar.Item.Gbx", which can potentially break records in case anything is tweaked in future.

Now to load the items:

Method one - force archetype/item for the map
This way the model is bond to the map, as usual for environment mixing maps. My templates do that on raw archetypes.

Method two - force via game mode
This is superior way if you want to force the car on maps, which don't use it by default, want TMU cars to have varying skins or want to add car selection (Pursuit does that for example). You gotta modify the game mode tho and upload it to the dedicated server.

Here's a set of templates so you can create your own tracks with the TMU cars. Unzip these into your Maps folder.

Use a multi-environment titlepack to open the templates in the editor. Bear in mind that you won't have the car models, only the physics.

riolu has a little demonstration here on how to use items to do it.

I notice that the d/l only has templates for Canyon, Lagoon, and Valley...no Stadium?

While I think it's awesome that Nadeo made importing those archetypes possible, it's a shame that they didn't just...*do it*. IOW, proper models, sounds, etc. in an actual pack.

Yeah, I know it would have been a lot of extra work and testing and so on, and that the community will do it eventually, now that it's possible, but...eh.

Either way, progress is good, and this seems like a great update!

I believe you can mix the TMUF archetypes into Stadium using OpenPlanet, just like you can use it to mix the other TM2 vehicles into Stadium with it.

Arkive says:
I believe you can mix the TMUF archetypes into Stadium using OpenPlanet, just like you can use it to mix the other TM2 vehicles into Stadium with it.

I've held off until now re: doing anything with OpenPlanet, because...well...I'm lazy.

Oh, alright.

*downloads*

TMOne Speed has been updated to use the Desert car. If you want to play Desert in TM2, it's definitely the best way to do it. And you can get it free in the ManiaPlanet Store in-game if you own Valley.

Note that the solo campaign still uses the modified Lagoon car gameplay, since those maps were designed for that gameplay.

But new maps created in TMOne Speed will use the original Desert car.
I've rebuilt a few Desert maps from TMU using the updated titlepack:
[Bad Track/Map Link]
[Bad Track/Map Link]
"UL7 Bäh! by XR'tmjooonas"
[Bad Track/Map Link]

Any update on all this stuff? Is it possible to embed a TMUF car with its model/sounds now in a TM2 environment without having to download anything else than the map (and maybe some files that'll be automatically downloaded with the map)?
And if yes, how?
Edit : I guess using the TMAll TP is the solution here ^^.