A few others also play on 3/4G I think. Drumchapel FP at the Donald Dewar, a few clubs such as Hamilton FP and EK YM, use Hamilton Palace (whether that's the artifical surface I do not know). Broomhouse use the Greenfield complex 4G. On the other hand, the occasional enclosed Junior ground is being used such as Overtown Thistle at Stonehouse. Balmore have moved on from there to a public park in Law.
At the end of the day, the Caledonian League is losing members to the Central Scottish on an almost annual basis. The Scottish AFL likewise. To attract / maintain teams, they're having to adjust their standards I suppose.