As @Keith_Beddoe has already mentioned, in an apartment block of flats, the owner, whether it be the freehold owner, landlord or managing agents for that property, would have had to have Openreach come around and survey the building first, then they would have to sign a wayleave for Openreach to install fibre.
Read Openreach PDF file about it here.
As you state the other property attached to yours is split into flats, does your landlord own the attached property too, or is that owned by somebody else?
If it's owned by somebody else, then this might have already happened, and therefore Openreach would be able to install fibre.
However, as your property is owned by a seperate party, then Openreach will only have a wayleave setup to install fibre at the property attached to yours.
Their signed wayleave should not include Openreach installing fibre anywhere on your landlords property without his prior consent and signed off wayleave too.
If however, like has been mentioned already too, that the two semi-detached properties here were originally houses that have simply been split into flats.
Then most likely, Openreach will probably be classing them as houses and not an apartment block and will be free to install fibre without any prior signed wayleave.
As you state one of the tenants in a flat in the adjoining property has simply just requested it themselves, then that would not happen unless it is just being classed as a house, or as before, a wayleave has already been signed by their properties owner or agents etc.
Although technically, if the tenant of this property doesn't own the flat, then they should still have had a wayleave to install it.
https://www.openreach.com/help-and-support/obtaining-wayleaves#:~:text=When%20do%20we%20need%20a,pro....
Also, note too, that on the link above it mentions about flying wires, which could be going across your property.
These are wires which “fly” across one property from telegraph poles on another property. We’re sometimes allowed to install these without needing a wayleave, but only if:
- we don’t need to enter the property to do it;
- the wires are 3 metres or more;
- they don’t interfere with normal business at the property.
Others have had the same issue like here, and many more will in the future too.
https://community.bt.com/t5/Archive-Staging/Flat-amp-Fibre-Installation-problem/td-p/2196049
https://community.bt.com/t5/BT-Fibre-broadband/Fibre-Connection-to-Flat-Block-next-door-is-connected...
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