Stock is worth zero, but good employees will get retention packages to stick around with the new company.
Maybe. Often acquisitions are just for the customer list. Betfair is located in London (and Dublin for tax purposes IIRC), it has no office in Scotland.
A 6-7 figure stock-based retention package would seem normal for the 3 acquisitions I've been through. Vesting length is all over though (short as 1 year, long as 4).