The answer is "sort-of" it depends which items you want, and which service centre you deal with. Some are more accommodating than others. All the software parts of the tech package can be unlocked for a fee, and some of the hardware parts can be added for a fee (some more reasonably than others)
As others have pointed out though "tech package" varies by year, so different features were, or were not, part of it at various times. A quick list of some of them:
- Navigation, can be added by software for a fee
- auto-presenting handles, can be added by software for a fee
- parking sensors, can be added, but are very expensive as they need new bumper covers, and, sometimes, a new wiring harness
- fog lights and LED cornering lights, can be added, simple swap of the modules and software update
- power lift gate, not sure, but I would suspect this one would be prohibitive
- lighted door handles, don't know.
- GPS enabled homelink, don't know
- HID headlights, can be added for a fee
- auto-dimming mirrors, don't know
- power folding mirrors, don't know