Water Usage in Rented Properties

We have been trying to clarify the issue of new leases charging for water usage.
The sound track of the OFT video says, for new leases, "Landlords will need to install water efficiency measures in their rented premises before starting a new lease if they want to charge their tenants for water usage."
For existing, pre-31 Jan 2011 leases, the owner is allowed a year to implement those measures. But it seems there is no such flexibility for leases signed since then. The wording implies that there is no way of subsequently implementing the measures and bringing in charges for water usage. So if the owner can't get the work done before the tenant signs the lease, there will be no reason to improve the property later. Is that what the conservation people want?