There are really two questions here:
- Can your connection support this use-case
- Will BT take any action against it
On the first question, with "a few hundred players", you could be hitting up against the bandwidth you have available. The key figure here is the 110 Mb/s upload figure, as that is what your server has available to send updates to clients. It depends heavily on things like mods you have installed and player behaviour, but estimates I've seen range from 50 kb/s to 0.5 Mb/s per user - at the top end of this, with a few hundred users you are starting to use up all your upload bandwidth.
As for the second question, if you are using up all your upload bandwidth for a reasonable chunk of time, then it is possible that BT would say you are in breach of the T&Cs as posted by @Madpeter - whether this actually happens depends on a number of things: how busy your local PON is, whether other users on the PON complain about poor performance, how much BT can be bothered to investigate those performance complaints and so on.
I would suggest you try it with a much smaller number of users (a few 10s as opposed to 100s) and measure the bandwidth usage over a period of time. Then you'll be in a far better position to know how close you'll be coming to limitations, impact on other PON users, and likelihood of unwanted attention from BT.
