The disability income benefit (if you become disabled before the age of 60) is only paid once you have been disabled for a period of 6 continuous months. (You will need to rely on your sick leave to "bridge" this 6-month period to the greatest extent possible.)
If, after the expiry of this 6-month period, the Insurer considers that you are unable to perform your work with Council in your current occupation, you will be entitled to a monthly income of 75% of your pensionable salary.
After a further 12 months (i.e. 18-months after you became disabled), the Insurer will re-assess your disability, but this time against a criterion of whether you are able to perform your job, or any similar job that you could do by virtue of your experience, training, education and age, with any Employer.
Only if the Insurer considers you to be disabled (according to the definition) would the benefit be paid.