Can current be drawn from ground in a SWER transmission setup?
Provided that the resistance of the load and the leads to the taps is comparable to that of the earth path in between this could work.

However that may not be practical to achieve unless the soil resistance is high.  Likely most high-resistance cases are local problems at the terminal points, rather than poor conductivity of the planet itself, so the "tap" might have to be within the local zone of one of the terminals.

Similar situations with more resistive return paths can be demonstrated (or encountered as safety problems) - salt water for example.