When operating on a LJR your usually in a tactical formation (in spread by 1.5nm) & flying at 480kts G/S or what ever you need to make the time on target, i.e. much faster if you've been bounced by the defenders. Don't worry fighters have very good radars & they are constantly searching ahead of then at a significant range from the ground up to 60,000ft, yes they will be able to paint you in your recreational a/c. Can't speak on behalf of the B111.
The first time I saw one up close was in the Atherton Tablelands, I rang the airforce about it and was told it would not have been there, so where is a LJR? my answer would be everywhere. It happened another time at Childers and I was told the same thing "it wouldn't have been there". It appeared as though these guys were going where ever they felt like.
As for your comments about radar that is not what the Air Force said, I was told the F 1 11 does not have a radar that can see other aircraft. I was told the pilots relied on see and be seen to avoid other aircraft. All this at 400 kts and low level it is a wonder nobody got taken out by these cowboys.