I'll tell you what I know, but I'm not sure it will be useful. I flew into Ontario once and out twice in December. This was when the MMW scanners were first installed; in fact, when I arrived in Terminal 2 there were no scanners; I was surprised the next day when departing from Terminal 4 that there were scanners; and ten days later, Terminal 2 had them as well. I was lucky though; the scanners were roped off both times.

If the scanners were to be used, however, I didn't see any way that one could avoid them. Each terminal has two scanners as well as two WTMDs. The scanners and WTMDs are next to each other.

That was my first time at ONT, and it looked like a nice airport. It's too bad that it probably will be my last time due to this "enhancement".