What about other rights of the employees/researchers guaranteed to them on the basis of a collective bargain agreements (such as the cost of travel to and from work or a fixed-amount financial help during long-term sickness or a Christmas bonus)? Can those be paid from the living allowance category or the employer/host institution needs to top-up the grant in order to respect their obligations towards all employees?

The AMGA p. 390 refers to
“a monthly living allowance to cover the employment or fixed-amount fellowship (with social security coverage, including compulsory deductions under national law (i.e. gross amount))”