From November, mobile workers whose company has taken out a subscription with either BT Openzone or T-Mobile will be able to use both Wi-Fi networks in the UK at no additional cost.
The agreement helps to unify Britain's fragmented Wi-Fi market. Both companies said in a statement that the deal would benefit people who want to be able to work on the move.
Mobility technologies like Wi-Fi and 3G offer big advantages to companies who want to boost productivity by letting employees surf on the move and have remote access to corporate IT systems.
But this comes at a cost. BT Openzone recently slashed its prices, but a single monthly subscription of up to 4,000 minutes costs £25 plus VAT. An occasional user will have to pay £6 for a one-hour voucher.
T-Mobile's Wi-Fi subscription, which it says is aimed at 'larger companies', costs at least £30 per user per month, with a fair-use cap of 5,000.
Back in July, Openzone hinted that it was pushing for a deal with T-Mobile.
Thursday's deal between T-Mobile and Openzone only applies to their UK hot spots. Both companies are members of the Wireless Broadband Alliance, a similar roaming deal covering Europe and the US.
Over the past two years a swath of Wi-Fi operators have engaged in a land grab for the most attractive locations in the UK, such as airports, hotels and retail outlets.
Because few locations in the UK offer more than one hot spot, companies need to check where their workers are likely to be before signing up. Thursday's deal makes this task easier, but some firms may find they are better served by a Wi-Fi aggregator such as iPass which provide access to multiple networks through one subscription.