label grouping should group by label text AND by symbolizer

The following is from my nabble post:

I am labeling roads.
When I use <sld:VendorOption name="group">true</sld:VendorOption>
the grouping appears to be based on the label string alone.
This would be fine in many cases, but not the case I describe here.
Some of my roads have the same name across multiple functional classes.
For example, 10th street is class 4 along one section but class 3 along another section.
When I label 10th street, the group fails to account for this problem.

See attached image: example.jpg

Looking at "10th ST", we see that the line is blue and orange (class 4 and 3)
yet the only label is blue; as you can see it is on top of an orange street.

See attached SLD: 900913_map_stclines.xml

The full nabble post, with minor comment from Andrea, is here:
http://www.nabble.com/textsymbolizer---group-is-grouping-across-road-classes-td18327306.html