Clever indeed. At 48V input they have to dissipate roughly 30V per color light.
I think you're right there. 0,3V means almost no margin to handle anything.
I would love to do so but the problem is that I can't find any step-down buck converters and MOSFET boards which can handle such voltage. Readily available are boards taking 36V maximum. Sadly I can't power the LED PCB at that voltage without replacing all the resistors (or indeed doing a lot of re-wiring to split up the LED strings) 
Are there any good MOSFET boards and step-down bucks out there that handle 48V well? I did find one buck but it was so huge it couldn't be fitted in the traffic lights housing..
What I'm looking for are boards with a small footprint like these (product pages are in English):
- https://www.tinytronics.nl/shop/en/power/voltage-converters/buck-(step-down)-converters/robotdyn-dc-dc-adjustable-step-down-buck-converter-lm2596-3a
- https://www.tinytronics.nl/shop/en/switches/mosfets/high-power-mosfet-module-5-20v-10a-4-channels
If I can find those capable of 48V, all my troubles are over 
Or am I possibly missing another solution here that's not yet been discussed?