Encryption is just maths, it takes no effort to add a bit of maths into the data stream. I also must say I'm surprised that your system over there is so silly as to make such radical changes to a costly radio system because somebody streams their contact. The fault, if it is one, is transmitting in the clear when anyone can legally listen in. If they wish to stop this for operational reasons, then digital is the way, but here, budgets, funding sources and systems management mean that shifts of this kind are 3 year+ projects, and no Police service would spend this money just to stop streaming. Here in the UK, streaming of airband is not allowed, and doing it gets a request to the internet service provider to simply pull the plug. Our emergency services have been encrypted for a long time now, and Police, Fire and Ambulance traffic is not available to the public, let alone streaming it. Seems to me, your system of openness so protected will simply go whenever a new system is installed, and somebody ticks the check box - encryption.
To be honest, with current issues, I'm surprised this hasn't been accelerated.