Reuters reports that the three companies plan to invest around $2 billion over the next 10 years in the joint operations.
MPT is a state-run operator and is currently Myanmar's telecom regulator. But the government has announced plans to create a new regulator by 2015 as part of the liberalization of the nation's telecom sector, and leave MPT as one of four licensed telecom operators.
In response to this decision, MPT embarked on a search for international telco partners to help with the expansion. The company had settled on KDDI and Sumitomo back in January, but a complicated negotiation process delayed the formal agreement.
Recently-released statistics from Myanmar's telecom ministry show that following the liberalization of the sector, mobile teledensity has doubled in the past year, reaching a total penetration of 16%