Ray traced reflections are completely borked or intentionally limited (optimization) in this game. No reflection of other cars from player car. Not sure why Microsoft saw the need to release this in a unfinished state. Another 6 months to a year would have been enough iron out a lot of visual inconsistencies here.
I looked ingame, photo mode and replays and at least on PC with max RT settings, all the cars reflect each other.
It's just limited to cars within a 10 to 20 meters radius or so.
I can see my car on the other cars, and even other cars reflecting each other when overtaking closely.
I could also see my car and others being reflected on the angled windows of the Catalunya track.
Also, when cars are passing under a bridge, they individually reflect it, but they will also all reflect it once again when your car passes under it as the fallback cubemap includes it and is used on all cars.
Track elements in RT are limited to a certain radius too, you can see the RT/cubemap limit when looking down the windshield.
When in photo mode, pressing X while a car is in the center of the screen will make that car the center of the default reflection cubemap.
That cubemap is also used on the cars being reflected in the RT reflections, you can see it change when looking down the windshield to see the reflection of another car and pressing X to target the car you are looking at. If the previous target was another car, all the cars will have their cubemap updated, including the cars in the RT reflections.