This is all straight gold. So many great posts in here. First of all, the 3 to 1 rule is just ridiculous. There is no comparison.
Yes you can cross train with cycling, but it's not the same. It will help you aerobically but that is about it.
I've said it a a few times on these boards and I will say it again. When I was in good running shape, I could hop on a bike and do relatively well. I didn't have the power but I could go on hard rides, climb and suffer pretty well.
When I committed to cycling full time, adapted my muscles completely (I now race professionally); I lost all of my running abilities. I couldn't run within 1 minute of my old mile pr at this moment. I am in the best shape of my life, and I couldn't run a sub 5 minute mile.
To the guy who wrote about cyclocross. It's actually a super chill and fun environment. Come watch a big UCI pro race before you completely hate. Spectator friendly and lot's of beer. (road racing not quite as inviting)
To the guy who is cross training 15 hours a week on the bike and running 6- Good luck with that, while I find it hard to believe you're biking 15 hours a week. You're not setting yourself up for a good season. You should be running!!