If your track follows ROAR rules, the TBR bumpers would not be legal.
6.2 BUMPER RULES
6.2.1 Bumpers are not required in all classes, but when used, they must be shock
absorbing and non-metallic, with no sharp edges. For safety, rigid bumpers, such as
fiberglass and composites, are not permitted.
6.2.2 Front bumpers must be of at least 1/8” material (3/32” for 1/12). Bumpers will not
extend forward of the body except on off-road cars. The bumper may not extend to
the side beyond the outer edge of the tires.
6.2.3 Rear bumpers must be made of a solid material with rounded edges and may not
extend to the side beyond the outer edges of the tires, and may not extend beyond
the rearmost part of the body except in off-road vehicles.
I would think that even if the track was not governed by ROAR, they would not allow TBR bumpers for the same reason as ROAR. Getting hit by an 1/8 scale with a TBR bumper could potentially cause severe injuries. TBR bumpers do not have round edges, nor are they shock abosorbing. I wouldn't run one anyways, it's one less thing to get caught on the track.