My lab has been storing their PC 12 cells in the -80 freezer... upon arriving here and investigating a new project I see that it specifically stated to be stored in nitrogen vapor? Is this the absolute case or is -80 for short term storage okay as well?
The temperature at which nitrogen evaporates is about −195°C. Given the considerable difference in temperature between the current freezer and nitrogen vapor, I'm inclined to say probably not.
I suspect that it may be dependent on what exactly you are using the PC 12 cells for. Without knowing more detail about the situation, I would do my best to get ahold of some liquid nitrogen for your samples as soon as possible. When in doubt, it is always best to follow procedure.
Until you can acquire nitrogen, -80 is still far better than room temperature. Be sure to take note of the discrepancy in your notes and hope for the best.
From talk among the powers that be in my old lab, many of the common cell lines have become divergent anyway. I think HeLa cells were notorious for behaving differently in different hands due to different storage conditions and culture mediums.
PC12 cells were believed to be similar, so I think that whether or not it's OK will depend on what you want to do with them. If you want to set up simple assays for comparing the effects of small molecules, then you'll probably be fine (obviously note down the storage conditions when starting your cultures up again).
However, if you want to replicate a differentiation procedure from another lab exactly, then you should be replicating their conditions as exactly as possible. Therefore your -80 stored cells might not be OK for that.
So as Astrolamb said, have a go, see how they behave, but maybe be prepared to beg someone to give you some more if the -80 ones don't do what you want them to.