Good news is it looks like you don’t have SE blocks. I don’t have a lot of experience with pivCLASS readers, though based on the name I’m assuming it’s a multiclass reader that reads iClass and ProxPass cards. Supposedly ProxPass can be cloned to the 125Khz side of the NeXT or an xEM.
More info here.
If all the passes are pivClass, I’d fathom a guess that they’ll all accept a flexClass. I’d still get a blank iClass card to check. Better safe than sorry.
Also, those systems are super out of date. You might want to check with your ID office to make sure that they’re not planning on changing/upgrading their systems in the near future. (Sidenote: this is sadly from experience. My flexClass has failed and I still need to get it removed. I also found out the school is moving to an ID system that’s on our phones. Which I have many ranty thoughts about, but that’s for another time, not even including the fact that my flexClass will be useless next year anyways. Sigh. Learn from my mistakes.)