I have never been upgraded from ET to CE though I tend to book more CE than ET.

I have only once been upgraded from WT+ to J (LHR-JFK) (ironically the only time I've ever booked WT+). I have never booked WT.

I have been upgraded three times from J to F out of dozens and dozens J bookings. LHR-JFK, LHR-PHL and LOS-LHR if anyone is interested.

So a pretty low percentage. My father-in-law who has my gifted Silver status is over 50% for upgrades but generally books WT+ on JFK-LHR and often at off-peak times for business.