I've looked into it a bit, and your suggestion certainly seems more likely. SICAT (the specific cantilever type earmarked for TPE) has a max. span length of 74m, so I assumed the structures would be more spread out.
Based on the distances between Church F & York (8.77km Church Fenton to Colton Jn; 8.87km Colton Jn to York), the total distance is about 17.64km. Dividing that by 74m gives 238.4 structures over the entire length, assuming all structures are portals; they may well be a mix of portals, TTCs and single track cantilevers so you're probably right.