I didn't see anything specific in the page source about how the mining is actually happening, but I'm horrible at looking at page sources. I suppose if their system is sophisticated enough it could be stripping out the program that the site is bringing with it to mine? I don't know how the mining is implemented in the website to know how that happens, but now that I stop to think about it's probably a JavaScript based mining, but again I don't know and I'm horrible looking at sources. I'm just curious so that I can figure out a way to get it working at work I had hoped that since it was in a browser instead of a program on my computer that can be scanned for would make it work, but it looks like that might not be the case here.
The program will definitely require quite a large maount of bandwidth for it to function in mining (though I'm not specifically sure of this amount, but it'll have to tyr and keep connecting to your device every 100 milliseconds at least to check its status).
It's unlikely it'll be blocking the entire site as you then wouldn't be able t access the site at all.
And the script will either be PHP or JavaScript. It might be an idea to check the addons that have been added to your work computer such as NoScript which would interfere with this system (and normally be used to ensure staff don't download stuff that they don't want to and contaminate the work's computer systems and servers).