It seems over the top to have an investigation and threats of disciplinary action.
www.bbc.co.uk/news/uk-england-bradford-west-yorkshire-13108578
If the company really objects to a palm cross then surely they could just ask him to remove it. Unless he has repeatly ignored reminders not to have personal artifacts in his van, then it seems a bit heavy handed.
I think the tenant who complained is just plain malicious. Its not as if a palm cross was hurting anyone.
Would this company allow a muslim electrician to carry a prayer mat in his van?
I think that this company need to do a spot check to see that EVERY van is clear of personal artifacts during the working day.