Have you gotten your answer? It doesn't look like it to me.
If I am reading it correctly, you want to:
Use the existing battery box on the white chassis (AA batteries)
Not use the included IR motor
Not use the integrated IR receiver
You want to use a PF receiver and PF motor so that you don't have to handle two different controllers?
(I'm a bit of a newb, so apologies if I am stating the obvious - it just doesn't seem like the question was answered and instead focus was given to the line of sight portion of your question)
As an aside - the 7897 has grown on me, I'm glad you found one. :) I really didn't like the bugger at first, and the giant nose pieces don't sit flush on the baseplate, but they nailed the look of the ICE. The train looks much cooler if you add in some extra matching passenger cars and extend it out a bit. I would also suggest you mod the leading engine and make it windowless to give it a better look.