The simple answer is: possibly. Every chip is different and those that get overclocked by the manufacturers are often selected specifically because they are more likely to run more stably at higher clocks. You would have to buy the chip and overclock it to know whether that specific chip can meet the same overclock stably as the manufacturer overclocked chip.
Depends..... there are OC Editions and OC Editions.....
Some manufacturer's release what are called non-reference cards that have various modifications to the "reference design". Factory OC'd typically cards fall into 3 categories.
1. Reference Design w/ Slight OC - Here the manufacturer puts a slight OC on a reference design and depends on the built in safety factor to allow it to handle the OC betting that they won't have a warranty issue with this small OC but they can charge a few bucks extra for it.
2. Reference Design w/ Larger Cooler - Well truth be told it's no longer a true "reference design" once the card is modified in any way. But adding a larger cooler may give you a bit of a boost but the cooler cools the GPU not the VRM. The early GTX 570's were well known for this problem ..... the GPU handles the OC at a decent temp but after the smoke cleared, users found they had burnt out their VRM on the PCB. So while ya can get higher OC's with these cards, you won't get what ya can outta the ones on next category.
3. Reference Design w/ Larger Cooler and Beefed up VRM - Vendors solved the 570 OC problem by offering 8 phase and 10 phase VRM designs as compared to the reference 6 phase design. The 560 has a 4 phase reference design and vendors made this card the biggest seller outta last generation cards by making a card that you could OC the begeezes outta. MSI offered a 6 phase design on the Twin Frozr, whereas Asus and Gigabyte among others offered a 7 phase design in their 900Mhz cards. These buggers easily past 1000 Mhz mark and even 1070 (30+% over reference) was demonstrated here:
MSI even offered the 560 Ti in and 8 and 10 phase design with the Hawk and Lightning series.
In short, when ya read a forum post that spending extra money on a factory OC'd card is a "complete waste of money", take that advice with a pound of salt. While it's certainly true with category 1 above, that advice simply is "not applicable" to categories 2 and 3 above. If it's me, I'm only buying from category 3, but a little research is involved before ya can figure out what card falls in which category.
And make sure ya using latest available version of Afterburner. For some reason I simply can not fathom, I picked up 40 MHz w/ Beta 15 while maintaining the same temps.