The estimated annual cost of the special industrial buildings allowances for enterprise zones is published in the tax ready reckoner produced by HMRC each year. This is available at:
http://www.hmrc.gov.uk/stats/tax_expenditures/table1-5.pdf
The revenue yield in the first year after abolition (2011-12) is expected to be £15 million, followed by £50 million in 2012-13.