There's actually quite a few interactions, some of which are intentional ability interactions and some of which seem to be genuine bugs.
There's a great diagnosis of enemies being left behind and stunned due to slight terrain elevation differences close to walls (aka curbs)
here.
It's possible to leave an enemy behind by taking a trajectory in which they get caught on a surface while Abrams continues going, unfortunately I don't currently know of a clip or replay where this occurs.
There's also the possibility you execute a perfect Shoulder Charge and pass right through the enemy, as shown in a clip I posted
here.
I agree with the first two being inconsistent; but never experienced any inconsistencies with the latter two.
1.
Shiv's Slice and Dice: I've always thought Shiv was "ethereal" while blue during slice and dice. I decided to test this with Mirage's Tornado and got inconsistent results.
2.
Viscous' Goo Ball: After some testing in the practice range I can't seem to figure out a consistent method for determining whether the Shoulder Charge will carry him, or leave me stunned. I suspect this may be due to whether Viscous' skeleton is "facing" you or not, which changes regularly as he rolls around and bounces off walls.
3.
Infernus' Flame Dash: I've never experienced any unique interactions with this... He's fast and you will be on fire...
4.
Vindicta's Stake: Prevents the enemy from moving outside its radius. If they're tethered you can pin them against the wall, assuming that wall is within said radius. If you carry an enemy to the end of the tether they will simply be left behind, a good example of which can be seen in a clip I posted
here.
The one ability interaction I dislike and suspect may be a bug is with
Mirage's Tornado. If an enemy is being held by a friendly Mirage's Tornado then Shoulder Charge will usually be unable to collide with said enemy, but sometimes will pull them behind you for a bit. A good example of it can be seen in
this post.