This band are...

It's well known that some noun phrases that are grammatically singular but semantically plural (like the government, the staff, the band) can occur as the subject of either a plural or a singular verb form (with pronouns obligatorily matching the verb in number):

The government has said it will cut taxes.
The government have said they will cut taxes.

*The government has said they will cut taxes.
*The government have said it will cut taxes.

This is often said to be a US/UK thing, although you do hear both on both sides of the Atlantic. I noticed a restriction which I'm not sure I've seen discussed before, and that's how it works when you have a demonstrative (or a pseudo-demonstrative, a term I've just made up, for when a word such as this is used in a non-deictic way, as in "So I saw this band, called The Semantic Plurals, last night").

I think, and this is true for me though it may not be for everyone, that if you have a singular demonstrative determiner (this rather than plural these), you can't have a plural verb, it has to be singular to match the determiner:

??This band are going to be playing.
This band is going to be playing. 

But even more interestingly, you just can't have a plural demonstrative determiner - it's far worse:

*These band are going to be playing.
*These band is going to be playing.

So the semantic plurality of a noun can influence number on the verb, but not the determiner - the determiner has to match the grammatical number of the noun. This is presumably because the features percolate upwards and you'd have a clash at DP level if they didn't match.