Okay, so I did some research into this and here's what I found:
- The Yamaha drive offers enough power for many, but not all, ebike lights to be connected. For example, Supernova M99 Pro won't work -- that's my favourite bike light. But lights like the Lupine SL S or Supernova M99 Pure work just fine.
- To install the light, one needs to remove the protective plastic cover and undo two out of three bolts that connect the motor to the frame.
So I've ordered the light and the Light Cable to connect it to.
Update: did the entire installation process, here are the approximate steps I had to take.
- Step 1: remove motor cover. Also the step where I get unpleasanly surprised that the bottom plastic motor cover has a hole in it. I wonder what idiot thought of that... this is where all the dirt and mud will accumulate. This is insane. Reminder to self: tape it over. Haven't seen this level of insanity from Bosch.
- Step 2: unscrew two out of 3 motor bolts, loosen the third... also the step where I realize that those bolts are tightened with 22Nm of force. I did not, do not, nor will I ever own any instrument with a hex key that can apply 22Nm of force. This seems excessive and downright cruel and no, Bosch does not do anything as evil. Consequence: had to improvise a long handle for a hex key. Pretty sure I did not tighten it back to 22Nm, but I don't care. It's not going to fall off.
- Step 3: connect Bosch LightCable to the motor (there's no ambiguity regarding the port or direction) and run it to the handlebar. This was also annoying because Haibike has these black plastic plugs where the wires came out and naturally, there's no space for extra light wire. Had to clip away some plastic.
- Step 4: connecting wire to Luping SL S light... where I found out that Lupine does not mark the type of screwdriver you need for opening up the light. Furthermore, I watched their video where they suggested a Torx T5, so I ordered one, waited two days only to find that the light actually opens with a T6. Insanity! Also, they ignored my support request :( and when a manufacturer does that, well, they get blacklisted in my book.
To sum things up: the process of light installation is rather annoying, but manageable.