Hi all,
Rob it will give the same result as most other calcined clay product, it is very hard and physically stable so that it will probably have a more limited CEC than a softer product like Akadama. The trade off is usually between physical stability (calcined at high temperature) and CEC. At very high temperatures this process may differ in that the material may be heavily fractured or foamed, to give a high internal surface area (these are "Hydroleca" type substrates).
Moler clay is 80% diatomite so the cat litter will be basically fused silica (and have a relatively lower CEC than before it was fired), but it will be very stable, and won't degrade.
cheers Darrel