The owner was lucky. Unless things have changed it was Network Rail policy not to caution trains for dogs or other small animals on the line. Personally I always thought that a bit callous, particularly if there are people about to see the dog get struck by a train not to mention the risk of the owner being on the line trying to catch it. Avoiding delay minutes penalties (sadly) a higher priority than compassion.
Even when I worked for NR in the Control it made me very uneasy. Not least because of the dog is on the line, the owner might well be too so as a minimum you should caution trains through until Ops staff get there or the line is confirmed clear. However the brutish management at NR had one thing and one thing only on their minds - delay minute penalties.
Swans are protected by the Crown - despite being generally bad tempered hissy little so an so’s - which means the job gets stopped if one is observed on the line before a train clouts it. Hey, maybe that could be a scenario for random events in TSW!