It's broken, to put it simply. It's been broken ever since TSW's launch. The most common example of resuming a service from save would be that signals would malfunction and get stuck on red.
That is correct. If you shut engine down and save when you open the game save back up engine sounds like its running it emits smoke like its running, all switches/breakers are where you left them, So its not really running, it certainly won't move. To actually get the engine to start again you have to shut it off and restart which only works sometimes. As well as Any hand brake that has been applied is still applied but the actual animation reverts to its unapplied state.
I can honestly say that I've never encountered the problems described in this thread and, by the way, could not possibly count the number of times I have saved an activity and completed it later. I am a PC user and have to wonder whether such problems are endemic to other platforms. My only complaint about the TSW save system is that only one save can be kept at a time.