I've made some test with German mortar and:
1. Without any bulletins (control test) - works as expected
2. With recruit training bulletin (Mortar auto-barrage fires more accurately) - haven't noticed any major changes in barrage ability, but auto-attacks were very inaccurate and it was quite often shooting itself.
3. With veteran training bulletin (Mortar auto-fire more accurately) - same as before, but even less accurate (from my subjective view)
Haven't tested soviet mortars yet, but from what I've seen for Ostheer, I'd recommend not to use those bulletins (even one).
This Pony is always right.