I'm guessing you're from the UK? This isn't specific to teams. Any group is referred to in the plural in the UK and the singular in the US. For example, "the police is" vs "the police are".
Right, and as an American when I read British English it's not the use of "their" vs "its" that strikes me as 'foreign', it's the fact that as you point out, the names of groups take plural verbs in British and singular verbs in American usage.
I hadn't noticed the wider use of singular groups previously, but that does make sense when you point it out. I suppose it was just more obvious because we rarely see american analysis of football outside of the world cup.
The City Council is … The class is … The police are … The firefighters are …
The phrase "the police is" sounds so foreign to me, that I am almost certain I've never heard nor said it.