Why does the ground appear to be connected to the hot in a 240v single-phase circuit?
Red, black and blue are the classic colors for 3-phase power (other than wild-leg).  The color combination does not specify voltage; that's what voltmeters are for.    

An important factor is the lack of neutral.  In the U.S. neutrals must be white or gray.  It is illegal to "tape" or "paint" another wire color to be neutral, unless the wire is 4 AWG or larger.  Measure the voltage between each wire and ground/earth.  You should get a significant voltage if the wires are not wrong-colored. 

How well do you really know the wiring here?  Are you sure you don't already have 3-phase or maybe someone beat you to it and installed a phase converter somewhere?  Maybe that has since been removed?   No kidding, I have a 240V 3-phase converter at a 120-240 service panel, that panel's transformer is fed from 3-phase service which is literally 20 feet away from it.  The things people do!

Now, the red wire being grounded is just wrong.  However this could occur if the grounding system is not proper, or if the neutral-ground bond has failed.  (And I have one of those in a panel right now.) All it takes is one ground-fault to "lift the ground" to hot potential (or more accurately, lower the hot to grounding potential, lifting the neutral away from ground.)