£3bn is a lot of money
CISCO can develop and deploy new products for far less - however, it will take the best part of 18 months to get products to customers.
BT developed their own videoconference solutions at their R&D facility in Martlesham (with support of local electronics companies). If BT could do it, CISCO can definitely do it. Their brand will ensure large clients will be willing to trust the solutions they offer.
That said, the Tandberg systems I've used are very good and are available now.