Modern cameras store EXIF header information in the image file. Examples of stored information are shutter speed, date and time, focal length, exposure compensation, metering pattern, make and model of camera used to take the picture, and if a flash was used. It's impossible to alter these, unless the image was run through an image editor, where the EXIF header information is stripped once the image is altered in the image editor. To have an accurate time stamp, the camera's date and time would have to be set correctly, and the original unaltered image would have to be submitted as evidence.
You can learn all you ever wanted to learn about EXIF header data here.
If a cell phone can transmitt a photo realtime or delayed, then there could be irrefutable
evidence that it was not tampered with, if the received photo is stored in another device.
Also, phone company might have record of such file transmission and time for billing purposes.
I do not know, and in the end it won't matter anyway.