Implementing an ASTRO 25 trunked system is an enormous, complicated undertaking that involves quite a few pieces of hardware and software, all of which eventually come together to form a complete system. One does not simply buy a few repeaters and call it a day. The backbone of these systems is essentially a complex computer "core" comprised of servers, routers, switches, IP networking, etc., and that's even before we get to any actual RF components like comparators, repeaters, etc.
So while yes, it's theoretically possible to possess the abundance of skill, knowledge, and experience necessary to design and implement one of these systems, it's hardly feasible in the real world to do so without Motorola being involved.
You would also need to license features and software from Motorola, so it's hardly a turnkey operation where you just order the hardware and plug stuff into an wall outlet.
As a practical matter, the answer to your question would be "not so much, no".
Is there a point to this hypothetical question? Because honestly, it doesn't make much sense without any context.