A Customs Union & EEA+ arrangement or some other kind of soft Brexit is beginning to seem potentially inevitable, however slowly it could come.
Today, the Commons has rejected some soft Brexit proposals, but with the Trade Bill and EU withdrawal bill still to come back to the Commons plenty more times, this is certainly not seen as a be all and end all. Yesterday, among all the fanfare about a meaningful vote(still not sorted), an amendment re: Northern Ireland was passed. [I believe as part of Division 177 (Hansard, Parliament Data)].
This Northern Ireland amendment is notable because it is suggested by some MPs that it compels the government to more or less keep the UK in the single market. These statements were made by Dominic Grieve and Ken Clarke, and both agreed with by Keir Starmer. This is further explained by The Guardian, where the bill as quoted looks pretty certain.
The measures banned by this section of the bill include:
- Border arrangements between Northern Ireland and the Republic of Ireland which feature
- physical infrastructure, including border posts,
- a requirement for customs or regulatory compliance checks,
- a requirement for security checks,
- random checks on goods vehicles, or
- any other checks and controls
This describes access to the EU internal(Single) market. When paired with the likely implementation of a Customs Union(due to government failure or inevitable Commons decision) and the definite commitment to measures in Northern Ireland and Great Britain being identical, membership of the Single Market and Customs Union might be a realistic prospect.
Update (16/06/2018)
It seems that Customs Union and Single Market membership could well be likely. Business Insider reports that European Parliament chief Brexit negotiator Guy Verhofstadt considers this likely. He said this to British MEPs, and will be meeting with Westminster MPs to talk about this option.