How do you get the ABS sensors off?...
Well, I did it (at least on the front) tonight, and here is the info. The early bikes used Allen fasteners, the later ones used Torx fasteners. I have one of the later ones. The fasteners with their location and size are very prone to picking up road spooge that fills the recess.
The sensor is mounted via two Torx fasteners, to an adapter that is fastened to the caliper via another two Torx fasteners. One of the sensor mounting fasteners is visible. The other is buried behind the sensor, and under the head of the other adapter mounting Torx fastener. You may need to get a sharp pointed object in there to clean out the recesses first. You cannot use one of the "universal drivers" with interchangeable tips. (I had one by Mac.) The universal driver stems are too fat to get past upper adapter mounting fastener. What will work, are properly "sized" Torx drivers. The properly sized Torx driver stem will get past the adapter mounting fastener. I have one of these "universal sets of Torx drivers" that flip out from the end of the cover/handle. It worked quite well, since the stems were thin, and cover/handle provided enough leverage.
Those fasteners are REAL TIGHT. The adapter mounting fasteners, are Red (Stud and Bearing, HIGH STRENGTH) thread locked in. (I think that the only type of Loctite that is imported into Germany, or bought by BMW, is the red High Strength stuff, that is nearly impossible to break free. Every time I find thread locker on a fastener on the K bikes, it is the red stuff. And it is a bear to break loose. Every time.) And the lower hidden adapter mounting fastener, is counter sunk, so that if there is ANY corrosion, it is really locked in there.
The ABS sensor is fastened by two T25 Torx fasteners. The ABS mounting adapter is fastened by two T30 Torx fasteners. The early ABS bikes used a 4 mm Allen for the mounting adapter, and I did not check the ABS mounting.
To see, clean out, and get to the fasteners, it is likely you will have to take off the brake calipers. I did. Both of them on the front so you can see the fasteners and get to them. Then the job is just a pain, and not a PITA.
So, now you know, and don't have to go on a discovery mission of your own. As far as ABS II I don't know. I don't have it on any of my bikes. Good luck if you ever have to take them off.