Is 2 Rail Atlas 148 track the same gauge as 3 Rail O gauge track...

Yes, just different rail height. I use both plus the Atlas/Roco track from the 1970s.

Yes, I'm running all my 3-rail engines (all center rollers have been removed) and rolling stock on Micro-Engineering/Atlas/Signature Switch Code 148 2-rail track components.  ALL BPRC of course

I thought the pizza-cutter flanges would bottom out but they don't.  When I ordered my #6 switches from Brad at Signature Switch I told him what I was doing.  He said he would allow for the 3-rail wheels, but I don't know what if anything he did.  I don't see anything that sticks out telling me "3-rail only".

Excellent switches by the way.  I tried building my own and after seeing how well his worked I replaced all my homemade ones with his.  You get what you pay for, quality and non-problematic operation.

Here's some 3-rail rolling stock on old Atlas 2-rail switches...with a third rail added. Basically the only thing I did was to remove the guard rails adjacent to the frogs. These switches connect to standard 027 tubular, which I adapted by soldering an 027 track pin to the Atlas rail joiner (not the Atlas O ones in the photo, but the flat 1970's style ones that look like oversize HO scale joiners)

---PCJ