I Can assure you that the file in question does work.
The install is not for the faint of heart, nor does it take a rocket scientist to accomplish.
Download the aforementioned file from XDA.
Rename it "update.zip" without the quotation marks.
Place the file on your external SDCard.
From "Powered down state" hold volume down (left volume toggle) first, and then press and hold "power button" (at the same time).
Do no release either until you see a few lines of white text in upper left corner of screen.
Shortly afterwards you'll see the Green Android update Robot and a progress bar.
Let it go.
It will go to approx. 75% and freeze (don't phreak out). Let it sit there for 2 minutes at frozen state.
Power off your tablet, then power it on normally again.
You get to a screen that says it's configuring apps.
When finished it will boot into ICS, but lock up on you (once again don't phreak out).
Hold power button until device turns off.
Hold volume down (left volume toggle) first, and then press and hold "power button" (at the same time).
Do no release either until you see a few lines of white text in upper left corner of screen.
This time you'll be met with a New Android Recovery Robot (new android recovery was installed when you flashed the first time).
Let him do his magic, and when he's done, you'll be met with the screen below (taken with my phone as the screen cap on the device obviously cannot be used).
Sit back, be patient for a few minutes, let it reboot, and have fun with ICS on your A200
As always, flash at your own risk, and if you brick your tablet I am not responsible!!!