At the risk of being labelled a pedant - and as others have subtly pointed out - airports don't use an MLS, aeroplanes do.
And just to prove that this isn't a completely wasted post, there was one at Cardiff a few years back, maybe ten years ago. I think it was part of the same trial as resulted in the installation at Heathrow - might have been a different manufacturer's bit of kit to permit comparison. No idea if it's still there I'm afraid.