They're saying the two big factors are technology and business consolidation. A lease where the lessee's business is struggling isn't worth as much as one where the lessee is one of the big players.
It's one reason leases are commonly written as a series of 5yr options - any time an existing lease gets too far out in front of the market rents or the location becomes superfluous the lessee simply waits out the existing option term and calls it a day.
Another common thing the brokers were talking about is how often the lessees were violating the terms of their leases by entering into sublease arrangements with other carriers and siting additional antennae onsite without telling the lessor or passing those rents along. Some leases allow for the lessor to add more cell tenants and some don't, but most leases don't allow the lessee to make their own deals. one broker estimated that at almost 25% of all leases, which I find pretty hard to believe; then again, maybe that's so.
One common method of valuation the mortgage lenders like is simply tabulating the rents from the remainder of the current lease and the next 5 yr term and that's it - no discounting and no consideration of successive terms. As it happens, that method often results in about the same value as the contributory value of a cell lease (in this region) when it's sold with the realty.
Speaking of which, in this region properties with cell towers onsite often sell with the cell lease, so you can actually extract the contributory value from some of those transactions - call the broker and ask, or simply pull the cell income out of the operating income and cap the realty income at the prevailing rate. It's not pretty, but it's often fairly consistent. It's one method the mortgage lenders seem to really like.
Around here, many religious use properties have cell leases onsite - often more than one. Cell leases are almost always mentioned in listings when they're present.
I'm somewhat of two minds on this one because the cell brokers are saying one thing when they sell the leases separately, whereas the cell-goes-with-realty transactions often demonstrate a very different result.