For me, working with a high leg system was pretty common as we had a lot of them in southern VA, but the corner grounded system is a type I have not seen or worked on before.
I learned about them here and would have been completely baffled had I encountered one before I joined this forum.
There used to be a lot of corner grounded systems supplying irrigation services in this area, but they have converted all of them (in the 2 or 3 rural POCO areas that I do the most work in) to 3 phase 4 wire systems, most are 480/277, but there still is occasional full delta secondary (240/480 with 415 volt high leg) that you run into from time to time. I'm guessing those delta systems were once corner grounded - every one I have seen seems to be older equipment, may even still have a white wire in the center leg of the disconnect with a grounded conductor that appears to been added at a later time pulled to the disconnect.
Many POCO's used to provide conductors all the way to the irrigation equipment and you will find that when they converted from corner grounded system they buried an additional grounded conductor out to equipment - but it was a few feet away from the existing buried conductors which doesn't help with keeping impedance down when you have a ground fault problem, long distances alone are enough of a problem
When I was still a first couple years apprentice, we ran into a farmer that needed us to resolve an underground problem on a corner grounded system(480 volts to irrigation equipment). It was common in those installations for POCO to run three conductors on their meter pole to a three pole fused disconnect with the middle grounded phase "slugged" instead of installing a fuse. This guy told us he kept blowing one fuse and decided to move that "slug" to the position where the fuse kept blowing. He then later had to call POCO to tell them there was a fire at the pole top in the transformer bank
hmy:, but switched the "slug" back to it's original position before they came out.
480 volts to ground is not a good combination with unqualified people having as much control over the installation as irrigation use tends to have, and is probably main reason these POCO have abandoned such systems. The users get into enough trouble as is with 277 volts to ground on these systems, but at least with those systems there generally is no neutral loads so they get out of the situation of using an EGC as a current carrying conductor - most of the time anyway.