Back in the 1960's Oil Sites Road was a public road for it's entire length as I recall when I visited the Stanlow terminal with my father. This was long before the M53 was built so one of the problems was speeding traffic and a high level of accidents. The last time I visited the area was probably 12 to 15 years ago again to visit the Stanlow site, and I was surprised to see the the road blocked off beyond the entrance to prevent public through movements to the Elton roundabout. At the time I assumed this was due to some form of expansion of the site across the road, but subsequently it seems it is related to security and hence the restricted access signage on the roundabout which state stopping and photography is prohibited once you pass the inspection point. This is common in port facilities under the International Ship and Safety regulations and I think there may be similar signs at the Tranmere Oil Terminal site on the River Mersey as well as within the restricted area of the Port of Liverpool. Back to the Stanlow site, I doubt there are any residents living on the island between the MSC and River Mersey, apart from perhaps the ferry man/men who ferry visits to the three tanker berths at the Stanlow site which are located on the island. From personal experience the only inhabitants appear to be rabbits, hundreds of them judging by the droppings!
No, no-one lives there now and the houses were demolished when the last residents left. They were employees (and their families) of the canal company. The article I mentioned took across one of the last (or the very last) former resident. The ferry remains to allow people to get to the oil tanker docks and you can't just rock up and ask to use it! There is a YouTube video by someone who walked in from Runcorn along that thin strip of land between the canal and the Mersey.
Oil Sites Road appears to be privately owned from the eastern roundabout to a random point past the station. The old maps I found say Shell, the question is whether it was transferred to Essar along with the refinery. Beyond that random boundary, including the gate where the four barriers across the road are, is less clear.
There is reference as far back as 1982 of photographers being approached by security.
Diesel shunters numbers 10 & 8 busy themselves in the Reception Sidings of the Shell Oil Refinery at Stanlow on Mon 25th October 1982. This photo was taken from the footbridge over Stanlow & Thornton station, looking towards Ellesmere Port, and we were shortly joined by a number Shell security staff - from both sides of the bridge!!
(MagLad on Flickr.)
Or this one from 1995.
The station being situated slap bang in the middle of Shells Petrochemical complex always has CCTV surveillance , and as predicated, soon after our arrival, security did turn up to move us on. However with some negotiation, they agreed for us to take our pictures before asking us to leave.
(AJF1 on Flickr)
However I half recall there are planning restrictions close to major oil terminals due to the potential very high risk posed by a leak or explosion?
There was an extensive planning enforcement 'situation' regarding the former Shell Research Centre, the University of Chester Thornton Science Park since 2014, which covered a similar point. There is a comment in the paperwork along the lines of 'it is not ideal, but accepted, that there are residents within the hazard area'. That referred I think to Ince, I haven't looked where the boundaries extend to.