I'd say the BBC report is wrong.

Vodafone's report says:

> Under s.5 of the Intelligence Services Act 1994 (“ISA”) the Secretary of State may, on an application made by the Security Service, the Intelligence Services or GCHQ, issue a warrant in respect of any property so specified or in respect of wireless telegraphy. There is the possibility that this power is broad enough to permit government direct access to Vodafone’s network by the Security Services in some instances.

If the possibility exists then you bet GCHQ is using it. Sorry, your own country can listen into your calls :(