In answer to the question posed by the article, the reply is that anyone who signed up to, was promised or who was offered RPI index linking is most certainly being cheated by a unilateral switch to CPI which, it seems, cannot even be challenged in the courts. The only reason for the government to make the switch, and do it without any consultation, is to save money.
Let's face it, why was CPI introduced in the first place? It was because being selective with the comparatives and excluding such nasties as mortgage interest, rent, council tax and buildings insurance (all of which were rising too fast for the government's liking at the time) from RPI to create CPI was a clever little wheeze to partially renege on promises to protect pensions and benefits from the ravages of inflation. Did we all suddenly stop paying mortgage interest, rent, council tax or insurance? Of course not!
I would not put it past this government to be now looking at the components of CPI to see what the current nasties are which could be excluded from a third version of the index to bring the figure down even further and save even more money. That they are robbing the poorest section of the community of a valuable and necessary protection while the rich grow ever richer at those poor people's expense seems not to bother the government in the slightest.
Having said that, there are sizeable swathes of the community who have been and are continuing to be forced into pension arrangements without any inflation protection at all and where the pensioner takes all the investment risks. If they have any length of retirement at all they will feel the pain of that in years to come as inflation progressively reduces what might have been a decent pension on retirement to a pittance. At 5% pa average inflation the purchasing power of your starting pension will be reduced by about 2/3rds over 20 years. Try living on that! Let us hope for their sakes that the predictions of a sudden and sustained major fall in inflation soon are correct.