The B16 carries air east of McDonald, this new LIMITED will serve more areas and have more connections to faster subway lines. If the B43 carries air east of Prospect, then that portion will be discontinued.
The B67, how I see it, is basically a B69. No point in having duplicated service where it isn't needed, hence the entire route being discontinued. The B16 will serve more riders while also being a LIMITED, so it won't get in traffic as much. And it will terminate at Atlantic, away from all of the worse traffic conditions.