What is the maximum amount of different bacteria in the drinking water in Europe?
No, your colleages are right: There should be no coliforms in drinking water in Europe following the Council Directive 80/777/EEC.
This PDF from the Northern Ireland Environment Agency (which follows the directice mentioned above) shows this a bit nicer.
It makes sense, since coliforms are a sign of mixing sewage and fresh water. Nothing you want to have happening.

This is the relevant table from the linked PDF:

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