You can see the air filter on the carb, so not turbo, but it looks a bit like a Cavaliar D intercooler. Looking at the plumbing, 1 hose goes to the oil filter housing. It looks like an oil cooler. Bit of a funny place to stick it.
Definately being used as an oil cooler, but if it's a standard intercooler from another production car, is it designed to take the sustained positive high-pressure of a Mini oil system of up to 80 p.s.i.?