Actually we can know and will know more easily soon. Non-comms are measured just like any other station that is recorded in a diary. Arbitron chooses to only publish ratings for stations in the commercial area of the band. The information on non-comm ratings is available in Maximiser (sp?). Since K-Love is on a commercial frequency at 101.9 (and soon 101.7) they will be listed in the "book" (or virtual book now). I can't remember exactly when they took possession of the frequency, but I'd think there would be results soon.
Also Arbitron is publicly publishing ratings for non-comms in PPM markets. Indianapolis converts to PPM sometime in 2010 so we should see all the non-comms.
As for the original question. The Walk has a very, very limited signal in a spot that is not easy to stumble upon. 101.9 is very viable and EMF fills the problem spot of Hamilton county by acquiring 101.7. That frequency covers the NE corner pretty well. Based of the decent numbers on The Song with a limited signal a while back, I'd theorize that K-Love will do pretty well in Indianapolis.