That would indeed be convenient, though to my knowledge this is the first time I hear of a way to specify the command timeout in the connection string. In all other cases one can specify timeouts, but those are always for the connection itself, not for commands.
If you set the command timeout to 0 in your code, it won't be set in the dqe (so leaving the default the ado.net provider will set), so it should take the command timeout set in the connection string, as I assume the ado.net provider will set it when commands are assigned to a connection with the value from the connection string.