At the moment I assume that there is no native way to do this, correct me if I'm wrong.
So I wrote a little script that will interpolate (not smooth) tilts of the selected points linearly:
curve = bpy.context.object.data
# create point list
points = 
for pt in curve.splines.points:
starttilt = points.tilt
stoptilt = points[-1].tilt
# linear interpolation
increment = (starttilt - stoptilt) / len(points)
for pt in points:
pt.tilt = starttilt - increment
increment += (starttilt - stoptilt) / len(points)
This will loop through the selected points and set the tilts to interpolated values between the original tilt of the first and last selected points.