I have heard of BMW's where the ABS unit has failed due to corrosion , when the DOT4 had been changed by the owners , but the "old" fluid remained in the ABS circuit.
That's the big trailie GS things , ridden through streams etc etc
As with HD , supposedly the "best" way to change the brake fluid on ABS bikes is with the Dealer Digitech involved.
I've been thinking of changing the brake fluid on my 2013 Breakout , the front was changed by Frasers 2 years ago while chasing a warranty ABS brake light in the dash.
They did hook up the Digitech at that time , saw it done. Fault turned out to be a broken wire in the harness at the steering head after all that.
Watching this thread with interest I will be !