ADSL is only run over copper pair (with bits of aluminium thrown in here and there to mess things up). You can't get ADSL over fibre. There are other technologies that'd run over fibre.
ADSL doesn't run over fibre but there are plenty of technologies that run over fibre to give you internet access. Zen will be able to tell you all about these.
What is it that you/your boss wants to be able to do - not from the point of view of "hat you have" but just what is it you want. And why does your boss seem to be keen on using the fibre (or seem to think it's the only way you have available to you as an option).
Simply having fibre doesn't mean you have to use it - there's nothing to stop you getting a dedicated (copper) phone line installed for an ADSL connection for example, the cost of rental of a phone line plus the ISP's ADSL cost on top of that will still be much cheaper than a leased line!