Back in the land of OZ and back a decade or so now when the situation was calm and stable, the union policy book had a clause that promoted an equitable intergration between the groups in the case of a takeover. Some time later a takeover was rumoured and did eventually happen, but in the period between the 'rumour' stage and the 'happen' stage the members of one of the groups, who had a significant majority in the union membership decided that 'equitable intergration' was not for them and pushed through an ammendment to the policy book removing that clause. Result: The minority group came out of it being pushed to the bottom of the 'new' list with restictions on what they could or could not do and the majority group gleaned all the benefits of the 'merger/takeover'.
So, when nobody was looking at an intergration situation Principles and Fair Play were paramount. When an intergration actually came along it was 'dog eat dog'. Human nature.... sadly !
And as far as concilliation or arbitration are concerned the result will only be considered a success when all parties are equally unhappy with the deal!