Why the EU banned the mercury free HPS lamps, if their mercury was removed for environmental reasons and their efficiency was only slightly lower than high pressure xenon HPS lamps with mercury?

The directives require certain efficacy figures to be met, otherwise the products are "banned" (here it means only their introduction onto the market, so manufacture or import, not the sale of existing stock already present within EU borders)

But I've seen many times the makers claiming some products were "banned", but in reality that was just marketing bull****ting on a fact they decide to stop that product (each maker has his right to stop making/selling any of their product they choose, but false blaming the directive is over the line).
Their marketing just wanted to discourage you from buying an equivalent product elsewhere.

I don't know the exact reason for the Hg-free HPS, but I have an impression the later case is way more plausible here...

It's a combination of both.

Most but not all Hg-free HPS lamps were banned because their luminous efficacy is lower than regular HPS lamps, and they fell below the minimum allowed efficacy levels.  It is possible to raise their efficacy slightly via a more complex design (although never as high as mercury-containing HPS).  It must also be remembered that the quantity of mercury in lamps is usually tiny, and that mercury is also released into the atmosphere from fossil fuel combustion and this is usually far more than the quantity contained in the lamps.  Life-cycle studies have shown that Hg-free lamps are actually worse for the environment, because their lower luminous efficacy results in greater total mercury emissions into the atmosphere than if more efficient Hg-containing lamps were used.  Moreover, the mercury inside the lamp is quite easy to capture during recycling, whereas the mercury emission from electricity generation is dissipated into the air over large areas and very difficult to capture. 

Therefore there is no strong environmental argument to use Hg-free HPS lamps, and because of that most manufacturers did not bother to invest in raising their efficacy to the levels that would have been needed to keep them in production.

How they compare in the Lm maintenance towards the end of their lifetime ? Do the Hg Free lamps have any advantage there ?

But the mercury free HPS lamps have a high xenon pressure, so how they are still less efficient than even standard HPS lamps. In your website , is written that mercury free HPS lamps, are slightly less efficient than super (High xenon pressure) HPS lamps with mercury, but still more efficient than regular HPS lamps.

In terms of lumen maintenance they are slightly better than mercury-containing Super lamps.  The arc tube is much longer than usual and the end-blackening around the electrodes obscures a relatively shorter portion of the arc.

They are indeed more efficient than regular HPS but less efficient than Super, due to a different spectral power distribution and greater thermal losses to the longer and thinner arc tube wall.  But they were phased out because the minimum efficacy for European HPS lamps was set at the same level as the Super models, so just above what the normal Hg-free types could achieve.

What is the intention ? The Hg free HPS is fairly good as it is, especially looking over the extended lamp life. Also, different manufacturers might have variations in the exact Lm figures of the Super lamps as well

Extremely pleased I voted to leave the horrid dictatorship EU! 🇪🇺

Why the EU banned the mercury free HPS lamps, if their mercury was removed for environmental reasons and their efficiency was only slightly lower than high pressure xenon HPS lamps with mercury?

They'd probably rather you use their beloved LEDs 

They'd probably rather you use their beloved LEDs 

yeah. sounds about right. although that technology is far from being as reliable in reality to a good old Hg-free SON!!

All things being relative, how "efficient" are the gas-lamps still employed in Berlin? Or have they been dismantled?