I know a few DBS drivers that were very interested in the prospect of a move to a warmer climate, doing the job they've done for years and making £100,200 or 300K all tax-free.
Then the paperwork came through....
The wages were EXACTLY the same (£49K or thereabouts) and it required a permanent move - no 'free flights home for holidays' and the like.
I know of only one driver still interested and the reasons for wanting to go have nothing to do with any earning potential.
I suspect the exact same position for signallers (and any other railway staff for that matter).
Don't believe the hype.
There is money to be made out there but direct employment by S.A.R looks to be the way to do it - a few employment agencies tested the water with offers of '$300,000 p.a tax free' - it was a way for them to get a list of potential employees to go hawking for business and some drivers spotted the figure, mentioned it in a mess room and it's now become fact.
Do some research before setting your heart on it.