AFAIK BOI own the land, which has had planning permission for housing for some time. The club own the buildings etc. on the land and anyone wanting to use the land would have to provide a suitable alternative pitch for WT.
As you probably realise, building houses is not exactly booming at the moment and with this extra complication BOI are as well collecting the rent and waiting till we vacate the plot.
I believe our current lease runs out shortly, but we are in negotiation to extend for up to 5 years (which should give your conspiracy theorists plenty of material to keep them distracted). The rent and running repairs/improvements to BV are not cheap. Which is why, relatively,NM will be quite a good deal.