I can't imagine a HTS can hold a candle to the image quality of a tech cam and lens. However, there is another issue here, which is workflow. The HTS allows camera control via Phocus and the iOS app (there may be an Android app too). For me, and the way that I work, this is the difference between needing an extra assistant to cock/fire the shutter or make adjustments to the scene/lighting. This becomes even bigger if you have lights that are adjustable via wifi (I don't, but wish I did). The HTS will provide sufficient quality for most clients and most projects. Don't under estimate the focal length multiplier, and remember that this come on top of an already small sensor. This may require stitching to get framing you require, which if that is the case, you might as well use a tech cam anyway.
So, yes, the HTS is for sure an alternative to a tech cam, albeit one that offers certain advantages (remote camera control, works with your existing system), and certain disadvantages (focal length multiplier, weight). It is certainly cheaper to buy or rent a HTS and see if it works for you that to buy/try/sell a tech cam. Personally, I think it comes down to available/disposable funds, intended use and how much you are going to use it. I do think the HTS can be a better option for architecture, but I think the tech cam wins for landscape. The big separation is the HTS is just an accessory for your Hassy system. The tech cam is an additional system that can use your Hassy back.