Yeah they are. FFT takes place west of Ordallia while FF12 takes place east of Ordallia.

http://www.uploadimage.info/images/80317ivalice.JPG Something like that I assume.

Also this is a timeline from the Ultimania book:



The timeline of Ivalice in Final Fantasy Tactics and Final Fantasy XII, provided by Square Enix's official guide book, Final Fantasy XII Ultimania Omega. Translation is as follows:

Final Fantasy XII History (brown)

* 1st Upper Box: Unknown Era - The Occuria reside in Giruvegan.
* 2nd Upper Box: Old Valendia 1 - Establishment of the Galtean Federation.
* 3rd Upper Box: Old Valendia 394 - The Galtean Federation breaks apart.
* 4th Upper Box: Old Valendia 706 - Final Fantasy XII takes place.
* 5th Upper Box: Several decades after Old Valendia 706 - Female St Ajora establishes a new religion.

Grey box: Are they the same person?

Final Fantasy Tactics History (blue)

* 1st Lower Box: Unknown Era - 12 Knights kills a demon, and rescues Ivalice.
* 2nd Lower Box: 1200 years before the Middle Ages - St Ajora establishes the Glabados religion.
* 3rd Lower Box: Unknown Era - A catastrophe befalls the civilization at this age.
* 4th Lower Box: Middle Ages - Final Fantasy Tactics takes place.
So FFT is like 1000+ years after FF12.