The organization 'Orchestras Canada' - a lobby group for Canadian orchestras, amateur or professional, has now discovered this library. OC keeps a master list of all the compositions in it's members' music libraries (at least those who are happy to lend to others). From their latest newsletter....
keep those parts coming....[IMSLP] currently hosts over 200 orchestral works with complete sets of parts and many more incomplete sets. I have added the complete sets to OC’s Inventory of Orchestra Music Libraries (IOML) database, which now contains nearly 6,000 entries.