Two easy changes to get your IF block to work:
1. You only need to do the Describe once; it returns a Describe object from which you can get the basename and feature type, rather than repeatedly returning to the feature class.
2. Use the ShapeType property of the Descibe object to determine if it's a polyline feature class.
Your IF block would start like this:
for fc in features:
Desc = arcpy.Describe(fc)
if Desc.shapeType == "Polyline":
outFC = Desc.baseName + "INT.shp"
outFC2 = Desc.baseName + "INT_sp.shp"
# and so on....