While the i9295 and the i537 have the same hardware, they have different software. More specifically, the i9295 has an unlocked bootloader while the i537 has a locked bootloader. What this means is that the i9295 is able to flash/install a custom recovery, custom kernel, and custom ROM while on the i537, in order to flash anything it must be signed by Samsung. Only official firmware is signed by Samsung, so there is no way to flash a custom recovery or custom kernel. There is a way to flash custom ROMs, but that's not important here.
To answer you question, theoretically you should be able to flash the i537 firmware on your i9295, but you will end up with a locked bootloader and no way to revert it. Your phone would still work and you'd still be able to use it, but it would be locked down so that you'd only be able to use AT&T firmware. If you really want 4.4 on your phone, I suggest you flash one of the custom ROMs in the development section.
If you still really want the 4.4.2 firmware on your phone, I'd be more than happy to trade my i537 for your i9295. This is a great phone and works great in every respect, I only wish it had an unlocked bootloader like the i9295. If I could do it all over again I would have bought the i9295 instead.
EDIT: I think
@mythi is working on a stock 4.4 ROM for the i9295, you might want to ask him about it.