I wouldn't be so quick to dismiss garbage trucks. They are a great way to bring the technology to fruition more quickly.
Motive: Garbage trucks must use HUGE amounts of fuel doing exactly the stuff that the hydraulic hybrid system excels at. These trucks weighing 40,000 pounds or more stop at every driveway of every house in every suburb, then accelerate to the next house. They need regeneration but can't afford to drag around batteries to store energy.
Ease of investment: Because garbage trucks are so expensive, the expense to invest in a new drive technology isn't as large of a burden compared to the rest of the vehicle. Also, it might be possible to integrate the existing hydraulic systems with the new one, reducing cost and perhaps improving performance.
Ease of maintenance: They also have fleet-style maintenance, necessary for supporting new technology...and their mechanics are already comfortable with hydraulic systems. I know that you insist that it's a low-maintenance system, but I have to believe that a new technology in its first real-world application will present some maintenance challenges.
More motive: They are fleet vehicles owned by large
companies with a big environmental image problem; people see waste removal companies as terrible for the environment, while the companies struggle to be
environmentally friendly and to make that effort visible. They need something like that and will pour money and effort into making the world know that they're using it.
I can totally see garbage trucks as a market entrance vector (if that phrase makes sense). It starts with garbage trucks and spreads from there, thanks to proof of real-world application and lots of marketing by waste disposal companies eager to shed their trashy image.