the real answers is: teams (a collective treated as singular noun) should use is.
HOWEVER- some collective nouns are treated as plurals, this is especailly true, (but not exclusively true) if they end in an S.
Finally--there is no way to know which collective nouns are exceptions--they generally are local idioms. (Local being used to define a variety of english, (UK, US, etc))

Dam'd if i can think of an example right now, but others will join in with more examples--hundreds...
and while most will be american (US) english idioms, not all will be. One has already been provided- (Arsenal)

my other obsession