Just like Apple has recently made their Apple SIM available to travelling LTE-enabled iPad customers, it looks like Microsoft may be looking to sell its own SIM cards and data service subscription to Windows 10 users with tablets and PCs that can accommodate SIM cards.
A new Cellular Data app will work in concert with the Microsoft SIM to access prepaid data services with no contracts or commitments and will use the same account that customers use to pay for apps on the Windows Store. It also appears that the service will only access data in the country where it was bought, no roaming will be allowed. It looks like Microsoft will limit the service to France, the UK and the US at first.
Source: Thurrott.com