There is not switching camera method on ICSLocalStream. However, ICSLocalStream could be initialized with an RTCMediaStream. That means you can fully control the video source of an ICSLocalStream.
Interface and protocol names start with RTC are defined in the WebRTC project. For RTCMediaStream, please refer to https://chromium.googlesource.com/external/webrtc/+/branch-heads/63/sdk/objc/Framework/Headers/WebRTC/RTCMediaStream.h. Thanks.