Remote deicing facilities have been in use at some of the major European airports for literally decades. Oslo, Munich, Vienna, Paris CDG and Helsinki are examples that come to mind
There was some discussion on the BA thread back in December, where it was suggested that LHR has provision for such pads even though they are not in use.
Its hard to see how bringing a couple of deicing trucks to a fixed location can represent cutting edge technology unless they are doing something clever with the run off. That having been said I agree it can certainly be a more efficient method than on stand de-icing.
The new Link Taxiway Z is presumably to facilitate access to and from the de-icing pad.