Just noticed these on the McLaren store website, are they a part of the normal TH collection or something entirely separate that TAG have produced just for McLaren to sell on their own? Both look like rather interesting Carrera line limited editions, the MP4-12C with big date is definitely on the pricey side at $15,250 possibly one of their most expensive non precious metal watches, but the Calibre 1887 1974 anniversary edition is a bit more reasonable. The MP4-12C is however bead blasted Titanium with a Carbon fibre dial, and what looks like a unique movement (McLaren call it a Dubois Depraz Calibre 4900 after the piggyback module, though the rotor is stamped Calibre 49).
They are part of the general collection. http://www.tagheuer.com/int-en/tag-heuer-carrera/tag-heuer-carrera-models The MP4-12c is really nice, but as you said expensive. The 1887 is tempting, but other models beat it.