Jim, to my knowledge know one has had to change throttle cables when doing this bar change.
You ask about the throttle and idle cables location adjacent to the brake line. Are they coming through the same hole in the fairing on your bike?
Originally the throttle and idle cables should go through the hole in the inner fairing. Not the hole in the fairing cap adjacent to the handlebars and brake line. If you need to gain a little length, however, you could relocate those cables to the same hole that the brake line goes through with the handlebars. It'll all fit and work fine.
Even though that might be a solution I'm still sitting here with no clue why yours won't work to begin with. Don't know of anyone else that's had that problem with just the bar swap.
Just call me "Lucky Jim", Don!

Throttle and idle cables go through the original hole in the inner fairing, brake line goes through beside the bars - just a question of what looks best there (I note yours is behind the throttle/idle cables, and Terry has his in front!

According to the venerable HD-Dude, in
http://www.cvoharley.com/smf/index.php?topic=18002.msg291833#msg291833"For the 575 bars on the EG models I would say that about 50% of the time I end up using +2" throttle and idle cables. There must be some variance in the routing and or cable lenth from the factory. The consistant thing about Harleys is that they are inconsistant...... "
I guess I'm one of the (un) lucky 50%!
Jim