If a server crashes, you will see the gameplay freeze a bit and the message “Server closed due to an unexpected error.” appears, then all players are returned to the lobby and the previous match is considered “no-contest”. If you are getting “Lost Connection to the Server” on the title screen, or “Failed to Connect to the Server” in the text chat dialog. That is NOT a server problem and instead is related to your connection to the game server. Yes, this can include situations where your general internet connection does NOT drop.
Unfortunately all disconnections and game crashes counts as leaving the match and will be penalized appropriately. The game server has no way to discern a legitimate disconnection or game crash from one that is forcefully caused by a dishonest player to bypass leaver penalties. You can learn about this policy here:
These games connect to different datacenters than that of Overwatch (obviously). Again if a problem is happening between you and the game server, it will only affect Overwatch. If you wish to find out exactly why your connection to Overwatch is dropping, consider running a WinMTR test. If you need help, the technical support forum is available.