I'm running Basecamp 4.1.2 on a Mac running OS X 10.8.3 and have a BMW Motorrad Navigator IV (same GPS as a Zumo 660). When I create a route in Basecamp and change the the via points created by dragging the route (while holding down the Option key) with the Selector Tool to Shaping Points those shaping points still get announced on my GPS while running the route.
Some might say that the Navigator IV's firmware changes don't support shaping points not being announced but here's the catch -- when importing a GPX file created using Map Source on Windows that has shaping points I do not get announcements of the shaping points. I import the GPX file into Basecamp and then Send to the Navigator IV and everything works as it should. I even edited the route in Basecamp after importing the GPX file and the 1 point that I created by Option-dragging the route was announced (even though I edited that point in the route's Via Point tab to be a shaping point) but none of the original shaping points were announced.
If anyone has any suggestions or if they can confirm that they too have or do not have this bug I would appreciate it.