The case described in the post (https://novaworkboard.wordpress.com/2014/03/10/an-unsuccessful-merger/) is the example of following the principle of not decreasing the welfare of the society. And I totally agree with the author that the benefit for the end-customer in case of merger between Volvo and Scania was at least doubtful.
As far as I’m concerned the critical issue in this story was the defining of the geographical market. And as it was described in the post the major role in truck sales plays the after-sales service. It creates several cons for defining the market as the global European one. The main is the necessity to use this service in the place of the truck exploitation, which leads to higher prices for the truck charged by the foreign dealer if you buy it abroad, as the dealer loses profit from after-sales service. So nothing stops the future JV in such countries as Sweden having 90% of total market share from increasing prices to the level of the near-by countries.
But I want to show the very different situation regarding competition on the truck market. 15 years after unsuccessful merger with Volvo Scania is being a newsmaker for one more time. Now VW, which already owns 75% of German truck producer MAN controls 62.6 percent of Scania via a direct holding and an additional stake, is owned by MAN. The VW started buying stock in the Swedish manufacturer in 2000 and acquired majority voting control in 2008. Though both companies have 27.4 percent of the market share in total making them the biggest player (compared with 22.9 percent for Daimler and 22 percent for Volvo) they are not as concentrated on any specific European market as possible JV between Volvo and Scania could be on the Swedish market. So VW won the permission from European Union regulators to buy the controlling stake, with the EU saying that it had no antitrust concerns. And transforming BIG 7 of truck producers to BIG 6 doesn’t seem to worsen the level of competition.
VW according to Swedish law needs to exceed 90% threshold in Scania shareholding to force the remaining owners to sell their holdings and delist the company. It is necessary for achieving synergy between the companies via integration processes as at the moment the minority shareholders of Scania refuse to share know-hows with VW and MAN preventing them from cost savings of about 200 mln EUR annually.  But doing this could increase the profit of the company and shareholders’ welfare, potentially decrease the prices for the end-customers for the product and increase the overall welfare of the society. But the minority shareholders do not do it waiting for the best price.
And till now VW hasn’t managed to reach this 90% of shareholding, which indicates that not having the ability to merger can also, bring the negative effect to the society welfare as sometimes having this ability does.