I suspect that this thread wasn't started to debate this but I'll have a go.
In the pre-Thatcher era of industrial relations there was inherent mistrust between management and workforce. Negotiations started with both sides making outrageous demands with no real substance and eventually after much time and usually some form of industrial action they would meet somewhere in the middle with a settlement that neither side was really happy with.
More modern enlightened thinking says that actually both sides want the best solution and, if there can be sufficient trust for both sides to put all their cards on the table, it is possible to get a much quicker and better solution for all concerned.
For management there are no real risks in this approach. Provided they are honest it will usually provide a solution that is acceptable to them and worse case the outcome will be only the same as if the old confrontation method was adopted.
The risks are all on the union side. If their membership don't trust management or worse, don't trust their union representatives, then the union will find it difficult to carry their membership however good the agreed solution and the effect on the union can be disastrous.