Joe,
Yes I have tried it. The problem is the th Tyros is a very poor MIDI controller as most of the panel switches and sliders do not send MIDI out and are not programmable.

So, you can certainly use them together, but not integrated
What's worse is when you select a registration, OTS ect the Yamaha does not have any 'external' setting so you can programm in the Bank/PGM Change messgae sent out when a user voice is selected. The Korg DOES have this feature and I use it.
It would be very easy for Yamaa to do in the OS.

When I called Yamaha on this issue (I had a T2 then) they said 'You don't need that, everything you need is in there and it is a home keyboard not a PRO aranger'

In all honesty..the Korg, while better still is not a full MIDI controller for a MIDI setup of multiple kbds/sound modules.

You might look at it the other way. Use the WS to control the arranger. A PRO WS has extensive MIDI capabiliy, you will need to some homework as to the required MIDI messages to control the aranger...and may need a PC involved as wel.

Another way to go: Use the WS on the bottem, put the arranger on top and just use them seperate. IF you want them close (like an organ) You will need some seperate MIDI mini controllers to control the WS as you will not be able to get to the switches, knobs/sliders.

One of the members here Vagro has done quite a lot and you could check out his work:

http://www.youtube.com/watch?v=8vClD9eMq10&feature=related