While preparing for my trip to Italy next month, I ran across this.
The paths seem to run all over the place and I am not sure how accurate they are but I thought someone might get some use out of it.
I can verify that the path that runs from Lake Maggiore past the airport does exist. This is a great path to head south from the airport. Only problem is that the path appears to turn East near AAbiategrasso. If you miss the turn over the bridge (once over the bridge the path jogs back west then quickly South East) you are headed back into Milan (ask me how I know ).
Also the one out of Cremona that heads NW is valid but it is very circuitous and the roads through that area are not all that busy anyway.