In this 5 player game, it appears to be impossible to reach the 8 house threshold for phase 2, so we house ruled phase 2 if all phase 1 houses are sold. Was that a good call? 
I'm told it's the Benelux version with new plants, and the other side of the board (Middle Europe) does have enough cities.
You have the rules wrong
In a 5 player game, 7 cities are required to trigger step 2. I'm finding it difficult to find an online copy of the official rules for the original (non-"recharged") variant, but here's the table from page 7 of my Rio Grande copy (copyright 2004, 2011 2F-Spiele):
The official Benelux rules from the Rio Grande website do not change the trigger conditions, so my current theory is that whoever did the "translation" of the rules into the Dutch version you have shown took some fairly large liberties they shouldn't have taken.
The Benelux map only has 5x7=35 cities, which is too few for 5 players. We should have played the Middle Europe map limited to 40 cities, but the house rule of starting phase 2 when phase 1 houses are sold out still made for a close and fun game:
