Forget all I said - it works somehow 
It works with either the customer condition or the in-operator but not both at the same time.
This means that I can’t do what is in my initial post but this works:
matcher: ‘isType(“Passcreator\Passcreator\Domain\Model\Pass”) && property(“Persistence_Object_Identifier”).in(“context.customerContext.assignedTemplateIds”)’
And this works:
matcher: 'isType(“Passcreator\Passcreator\Domain\Model\Pass”) && property(“customer”).equals(“context.customerContext.customer”)
But not this:
matcher: ‘isType(“Passcreator\Passcreator\Domain\Model\Pass”) && property(“customer”).equals(“context.customerContext.customer”) && property(“Persistence_Object_Identifier”).in(“context.customerContext.assignedTemplateIds”)’
I assumed the latter should work and will investigate more.