Is there need for eir to do a solo run?

Eir are currently laying a fibre optic cable in an estate in Dublin 14.

There is at present a Virgin Media fibre optic cable on the road.

The new eir cable is underground, whereas the Virgin Media cable is strung along the eaves of the houses and hence not at all as good a job as the eir cable.

But would it not have been a cheaper operation had eir piggybacked on the Virgin Media cable?

Isn't that what happens with out electricity infrastructure?