The engineering tinkers definitely stack with regular enchants now.
Tested it myself so I can vouch 100% that they do.
Whether this is intended or a bug though, I can't say.
*Mind Control Dish stacks with Helm enchants. Stamina on the helm tinker is still there, it doesn't say it on the item but it does add +45 stam
*Parachutes stack with Back enchants
*Nitro Boosts stack with Feet enchants
*Rockets and Haste stack with enchants (including the 250armour)