The 'poll tax' (= Community Charge) was replaced by Council Tax in 1993. I've never heard of any discount for people over 75 and the Government website makes no mention of it:
https://www.gov.uk/council-tax/working-out-your-council-tax
Your neighbours might be entitled to a reduction if they've got low incomes but that applies to everyone, not just to people of any particular age.
Similarly, I've never heard of any reductions council rents for people of any particular age (and there's no mention of any such discount on the 'official' and 'charity' websites I've just checked). However (like everyone else) your neighbours may be eligible for Housing Benefit if they've got low incomes. (If they're in receipt of the Guarantee Credit part of Pension Credit they might even be eligible to have their rent paid in full). See here:
http://www.ageuk.org.uk/money-matters/claiming-benefits/housing-benefit/eligibility/
So my answer to your 'True or Not' question is "Definitely not!". However that doesn't mean that your neighbours shouldn't investigate the possibility of getting some help with their rent and council Tax payments if they're on a low joint income.