a) Maintain integrity with the rest of the UK
b) Leave the customs union
c) Keep an open border with ROI
It's easy to get any two of these, but impossible to have all three without a contradiction. Which will be renounced? (Or rather, since this is a matter of diplomacy, which can most easily be dressed up in vague and ambiguous language to look like its opposite?)
I've no idea what was Mrs May on, thinking she could sacrifice a) when she's at the end of Arlene Foster's leash. b) is impossible for her too, because she's also on the leash of her own right wing.
Ergo, she will sacrifice c).
But no! Because the Irish government will veto further talks in that case.
But actually yes! Because ROI will be under pressure from the other member states, who want a deal, and will also be aware that if there is no deal a hard border will come into existence by default in 2019.
Also, c) is the most amenable to being dressed in vague and ambiguous language. Once phase 2 talks begin, the Irish lose their veto, and Mrs May (if she's still in office) will begin to backtrack by degrees. They don't call Albion perfidious for nothing - but actually, in this case it's the Tory party, who will sacrifice not only their own country to stay in power but also their neighbours'.