A number of those motors from the Garaiya (essentially a P12 20V) and gearboxes (6 speed RS6F51A) became available recently when a company that used to maintain them for a racing league went bust and sold off their spare parts.
Quite a few of those motor/gearbox combos ended up in australia (at least 6, possibly as many as 10-12?).
I dont beleive that is a btcc sr20 in the micra as it isnt a capless valve cover(ie btcc used custom magnesium valvecovers with no oil cap as the engine was designed to be dry sump), iirc it is just a 20v with a custom spark plug cover. Also if you guys like the asl you should check out the old tommykaira zz s it has a sr20de in it with quad throttles and its mounted midship style! they also had a zzII which had a MR rb26dett in it making one of the most intriguing exotics of all time...to me anyways