Transport for London are doing its bit.This is in no way a criticism of Sandi - she can do no wrong in my eyes. It's simply an observation on the oddity of English. She's started out with plural agreement (are), because TfL are semantically plural. Like I said, this is totally OK in British English (I think there's some difference between the UK and US on this, but I'm not sure what it is). But then in the same sentence, she uses singular agreement (its) because TfL is grammatically singular.
This variation is common, and speakers are often inconsistent in their use (I know I am) but it's unusual to see it in a single sentence.