Make sure Vias are available
After receiving help form Mentor tech support, I can now answer my own question. When using integrated flow, the following rule apply regarding via placement:
1) RMB->Via Type is a NOOP - it's still there but it has no effect on the type of via that will be placed.
2) The property window cannot be used to change the type of an existing via to any type other than that specified as the default via for the net class. Anything is else is a violation.
3) A net class can have only one default via type
4) To place a via of a type other than the net class default, you must first use Setup->Via Spans to change the default via - even if all the via types are "through"
Not exactly convenient, but it works.