From Tesla in 2007:
Limitations: Regenerative braking is necessarily limited when the batteries are fully charged. Because the additional charge from regenerative braking would cause the voltage of a full battery to rise above a safe level, our motor controller will limit regen torque in this case.
And from a Model S owner in 2017
I live on a mountain at about 1500 feet. To get to town, I have to drive 2 miles to about 1600 feet, then 4 miles down the other side of the mountain to almost sea level. When I leave home and my Model S is charged to its daily amount of charge (80% or so), I’m heading up the mountain to the top, so the regenerative braking does most of the work of deceleration, and my speed is mostly regulated by the accelerator and regen rather than needing the disc brakes, except for the steepest grades, sharp curves, or stops.
Then I get to the top of the mountain and head down. About half-way down the mountain, the battery will fill enough that I’ll notice that I have to use my brakes to slow down, just like I would in a car with no regenerative braking. When this happens, a dashed line will appear on the energy indicator to show that the regen is limited (of course, driving down a steep, windy mountain road, I rarely notice this, as looking down long enough to spot it could be fatal).
Note that the regen is limited long before the battery reaches full charge. The regen becomes limited at about where the battery was charged to when I left home. It does not get anywhere near 100% charge before I lose regen.
If I have max-charged the car for a long trip, I will lose regen almost immediately (the first part of the drive is downhill before I go back up), and lose it much sooner as I go down the other side.
At this point it is just normal driving for me, so I don’t notice it much (except at max charge).
Trains use resistors to dissipate the energy generated during regeneration and it is also possible to use a Supercapacitor, I believe. Neither I would imagine, fitted to the new Jazz.
From what I have read, the Jazz uses the energy, via the generator, to turn the engine, without any fuel supplied, exactly as my 2006 Jazz does with DFCO.