Have been doing some upgrades today on a job taken over from the original installer. He has speced some real strange equipment combinations ($5K JVC Receiver and low end Wharfedale speakers!) and I feel really sorry for the customer.
Only realised today after looking for a spot to plug my USB cable the MX-650 is an IR learn only remote.
There is a base station for RF in the system, sorry didnt check model number. I think it has six IR ports on the back, but i could be wrong. Will it work with the current URC range?
I want to give this customer real proper macros, not some half arsed point and learn maybe it will work rubbish. Is there an economical and reliable way to polish this turd or do I have to deliver the not so good message nicely?

You will want your laptop and another programmable remote nearby to inject some discrete codes into the 650.

It's slow and painful when you are used to the pc programmable ones, but is doable. I've done a few 450s lately and for small systems they too are doable.

I would however show him some better remotes so he has the option to go to something demonstrably better. His 650 is discontinued and likely his base station as well.

If the base station is a 100, 200, 250 series it is older technology and could be a real hassle. I personally have had good luck with the 250 in my area but that model has caused others to leave the URC camp in the past. If you are in an RF interference area, you may want to tell him his remote could be a time eater. I am presuming you are on the clock and want to warn him.

So the base station wont work with the newer remotes? I will need to spend hours learning macros into the system?
He has another one of these in his bedroom and sometimes the cable boxes will change at both ends of the house from the other system! Can they be changed to different ID or frequency?
The codes which have already been learned for the cable boxes (other installer) always send multiple button presses for the channels. This could be a real problem, because the boxes here are notorious for this. The lady of the house just today held instead of pressed the channel up button and sent the system into channel changing pergatory!
I think I know my answer and they are not going to like it....

It will "work" (as long as you're not talking "i" series remotes) but it won't work "well". It'll be missing all of the significant RF improvements that have occurred. If you get a new remote, get a new basestation.