I don't think anyone will put up any border posts anytime soon but that does not mean WTO brexit won't have huge impact on NI and ROI. Until now, they can trade tariff free and to a large extent, with little paperwork. From November 1st, all businesses involved in cross border trade with the EU will have huge admin problems.
I give you an example:
I have a customer in Jersey, Channel Island. He needs to send a part back to us today.
Guess how many forms I have to fill in on his behalf: 3 forms, properly signed, letterhead etc, stamps, recorded delivery, dig out the original customs declaration when we imported the part from China, pay Condor Ferries their admin fees etc.
Same again when we send him the replacement part.
Who would want to sell to EU customers after brexit?
Would customers in the EU want to buy from us?
Just imagine you will have to do the same to send a part from Belfast to Dublin and vice versa.
Even though the part from China has already been through the correct customs channels?
That is horrifically over bureaucratic. The EU should be streamlining this not adding to it.
I do maintain that the EU is actually terrified of a free market.