I asked the dealer once if this could be done factory-style, meaning installing the buttons and everything because I found a set for about $400 once, and I had some insurance money...but they said it would be too big of a job. So splicing them in or going with aftermarket ones are the way to go.
Plus where is the button for these boards on an LTZ/Denali? Our Escalade has them, and the button is by the power gas pedal button, but the dash layout is so different than Tahoe/Yukon.