I Googled the heading of the above article, and found a Unison info sheet from a University branch, which says the info is taken from the Unison Industrial Action handbook. The bit about SSP is quoted below -
Workers who are absent on sick leave when a stoppage of work starts retain their right to statutory sick pay during the period of industrial action. If an employee reports as sick on the day the action starts, the employer can be expected to make their own judgement as to whether they should be regarded as on sick leave or on strike.
Edit - I then found the IA Handbook itself, here
http://www.unison.org.uk/acrobat/17518.pdf see page 13 of the document.