From what the devs have mentioned, I'm under the impression that SMART is just a button that allows you to easily do slides, trick jumps etc at the press of one button. All the things that you can do with SMART can be done manually, they just require more key presses / timing.
This is essentially correct.
However, holding down the SMART-button (instead of only toggling sprint) does not allow you to simply slide whenever you want it. This still
requires the crouch-button. Only certain objects (such as the security-sensor at The Airport) allow SMART to act "intelligent".