Where can I find number & type of telephone sets in HQs?

If this is the case, then the index from Garry's search link gives the following file (not digitized)

OPERATIONS - EQUIPMENT FOR OPERATIONS - Corresp, reports, studies, charts, drawings, etc, re various army eqpts collected by BRA, 1st Cdn Army, d/20 Mar 44/12 Apr 45. - Minutes of 21 Army Group meeting at St Pauls School, 18 Mar 44 re provision and replacement of M7 eqpt. - Notes on Sabot projectiles, particularly the QF 6 pdr 7cwt Sabot Shot by 1st Cdn Army, d/15 Apr 44. - Vehicle Staff Tables for AFV's, certain "B" vehicles, Grens and Gun Towers, 1st Cdn Army, d/26 Apr 44. - Deficiencies in AFV's & "B" vehicles of 3 Cdn Inf Div and 2 Cdn Armd Bde as of 1 May 44 and of remainder of 1st Cdn Army as of 15 May 44. 1944/03/18-1945/04/24. File.
RG24-G-3-1-a. Volume/box number: 10467. File number: 212C1.2009 (D89).
Textual material. [Access: Open]. Government.
Finding aid number: 24-68-4

Notice the "Vehicle staff Tables" in the above, s you may want to check it out in your next visit

 

Here is a list with scale of telephones and equipment in the 2nd Army HQ (Forward and Rear) and the switchboard configuration

From WO 244/88