The SPLayMch command is similar to the LAYMCH (Layer Match) command, except that when certain Civil-3D entities are selected as the item to match, this command uses the "apparent" layer of the selected object, which may be a layer from a Style.
Type SPLayMch at the command line, and select objects on the layers you wish to isolate.
Unfortunately, at this time, the SPLayMch command currently only works on the following Civil-3D elements:
Primary Parcel Area Label
Parcel Segment Labels (not available in 2008 version)
General Line/Curve Labels (not available in 2008 version)
Parcel Segment Labels and General Line/Curve Labels (not available in 2008 version)
The way these labels are implemented in the API, each label may have two styles attached to it. One style is for Line Segments, and the other is for Curve Segments. Even though the label only displays one or the other, it always has both a Line and a Curve style attached to it. This can be seen by selecting the label and looking at its properties in the Properties Palette.
If both the Line style and the Curve style are set to display on two different layers, you will be prompted to select the one that you wish to match.
Similar to the LAYFRZ command, except will freeze (or vpfreeze, in paperspace) the "apparent" layer of certain Civil-3D entities.
Similar to the LAYISO (Layer Isolate) command, except that when certain Civil-3D entities are selected, all layers involved in displaying the entity will remain visible. Also works to isolate entire XREFs, or individual layers inside of XREFs.
Similar to the LAYOFF (Layer Off) command, except will turn off the "apparent" layer of certain Civil-3D entities.