It's more the other way round.
It's the exchanges with good LLU suppliers that BT are likely to WBC enable first, otherwise they lose a lot of the broadband customers at that exchange.
My exchange had several LLU suppliers four years ago. WBC enabled last year
in the first batch!
Samknows shows all published LLU and WBC enablement dates, but not all LLU suppliers reliably publish the dates.
For example, but it hasn't happened yet.