Hey there, great question! Localization is an important part of Overwatch and audio is just one part of that effort. When we're discussing new heroes, new maps, and lore, we make an effort to collaborate with our diverse global team early in the process. A unique aspect of localization for us is empowering our regional teams to help select voice actors and provide early feedback when we're working with content that is from their region.
In general we try to have VO in both English and native language, and tend to alternate which we use based on if the hero is on your team or the other team. There are logistical considerations, for example not all voice actors are multi-lingual.
Audio plays a huge role in Overwatch gameplay. Scott Lawlor, our audio director, and the rest of the audio team are extremely passionate about Overwatch. Their hardwork and creativity result in not a great overall audio experience but also nice touches like the piano in Paris!