Was speaking to a guy a few weeks ago who has a event venue in Northamptonshire with a lot of land, some of which has been subject to a CPO for HS2, who informed me that even if it doesn’t go ahead he is still due the statutory compensation. Presumably that applies to a lot of land along the proposed route.
For that reason, along with the fact that a significant amount of the preparatory work has been undertaken at both ends, I reckon they’ll press ahead with the Birmingham to London route, but cancel the rest, with the funds (plus) being diverted into intra-northern rail investment in particular.