As with many topics, ask a question and you will get many different opinions. There are experts who don't think a sprinkler system is always the answer and that may be true. However if you are a London Council and the London Fire Brigade recommends that councils do retrofit sprinklers to tall buildings it feels fairly safe ground to conclude its a good idea.  

For large tower blocks this is an HRA cost but affordability to fund this from reserves will vary considerably (increasing rents seems to be off the agenda to some degree and hopefully leaseholders aren't going to get yet another bashing).  The question is surely again one of a proper understanding of local government finance by central government.  

If a council has £10m in HRA reserves and sprinklers costs £10m it is not appropriate for all the reserves to go on sprinklers, given reserves must always be retained for future rainy day risks.  If on the other hand the Council, has £50m in HRA reserves, then perhaps its a different question. 

The Government have repeatedly stated that the safety of social housing " whatever the cost" is paramount.  I believe they need to stand by this clearly and fund these plans based on a reasonable assessment of costs versus resources.  Not everyone will need £10m and not everyone will have limited reserves but decisions need to be made in context.  Not sure it's rocket science either to work it out and we don't want delays over financial wrangling to be cited if we have another Grenfell.