Still, every network only buys X amount of bandwidth, per X number of customers.
Unless they have 1:1 and alot of hardware to share the load over multiple links I dont see how they could be certain for network pings not to rise / speeds not to slow as they claim.
For an ISP which supplies bandwidth to many schools and universities they should have bucket loads of free capacity during the evenings and weekends. They would have a double peak so to speak, one around mid day and then again in the evenings so they should be more than fine to handle users going all out on the weekend.
In fact I wouldn't be too surprised if you saw them doing this on a near monthly basis, doesn't cost them anything more and gets people into the habit of really using their connection which will hopefully result in more data usage over the rest of the month too.
Usually bandwidth pools are kept totally separate, as businesses pay alot more, and there are SLAs involved.