Hasn't the Devon ASU been flying (the pilots I mean) with gog's for some years? The Exeter boys were cadging used batteries off the Junglies at Yeovilton to save money.
Believe money's the main issue for the feds/Air ambo's - these things ain't cheap. The units' paymasters are tighter than two coats of paint when it comes to springing for stuff that costs much but delivers a relatively small increase in capability. Cultural lighting being strong where they tend to spend most of their time as stated above.