Train companies, lawyers and gas companies all spendingThree more companies have - separately - signed contracts which will see them upgrading to IP-based network technologies to allow them to use services including VoIP and videoconferencing.
Law firm Irwin Mitchell is spending £2m on a new converged IP network over the next five years.
Cable & Wireless will replace the lawyers' Frame Relay networks with new IP-based technology.
A managed wide area network will connect the five UK offices and underpin a firm-wide disaster recovery programme.
The company will also be able to introduce VoIP as a result of the new network, which will reduce the costs of moves and changes - deploying new phones to 350 people recently took five staff just three hours.
Gary Thomas, head of IT operations at Irwin Mitchell, said the firm has seen a significant improvement in the performance of applications such as its case management systems.
Rail operator EWS has also revealed it is spending millions on a converged voice and data network.
The network will connect 130 sites throughout the UK and is part of plans by EWS to expand rail freight services in Britain and mainland Europe.
Under the contract, BT will provide the network - which is based on Cisco technology - for EWS' 5,200 staff, supporting applications such as video telephony, voice recording and unified messaging.
EWS chief information officer Guy Mason said the improved network will create "significant operational efficiencies".
He said in a statement: "Effective and reliable telecommunications networks are essential for the 24/7 rail freight services provided by EWS, which form part of the supply chain for British industry."
Meanwhile industrial gases company Air Products and Chemicals has signed a "multi-million dollar" contract which will see AT&T furnish it with a global IP VPN, linking nearly 500 company locations in 30 countries.
The telco will convert Air Products' sites in Africa, the Americas, Asia, Europe and the Middle East so that they use multi-protocol label switching (MPLS) technology, which generally helps transmit data packets more flexibly.
The network also provides business continuity and disaster recovery capabilities for Air Products' three hub locations in Singapore, the UK and the US.