A report on the Hereford line signalling in Jan 1872 resulted in Saxby and Farmer patent gates were ordered for the level crossing at Marshbrook, Craven Arms and Onibury.
Most of these signal boxes were to a standard joint line design, very similar to the 'Type 1' Saxby and Farmer ones.
The LNWR took over on 01 Jan 1885, page 237, on 01 Jan 1904 Great Western took over the Shrewsbury District Lines.
Further changes took place on 01 Jan 1909 on the retirement of Mr Johnston in which the LNWR took charge of the Birkenhead District and the Shrewsbury (exclusive) and Wellington. In consequence the signal work of the latter line was transfered back to them. GW took the remainder of the Shrewsbury District.
This is a brief synopsis of Chapter 17 - Signalling on the Associated and Joint Lines.
This book would be helpful. Is most probably in the Society's Library one would assume.
Richard's statements in the books were taken from an extensive reading of the minute books of the LNWR (and the Joint Committee?). If necessary, references to the relevant minutes could be provided.
It seems to have been fairly usual on some joint lines for the maintenance to have been divided up by periods of time - ie GWR would fund, administer and organise the maintenance for 5 years, then the LNWR for 5 years and so on. This was seen as being fair to both joint owners. New Works were slightly different, but I get the impression that these were handled on a similar basis. On the S&H and S&W this resulted in a mixture of Joint LNWR and GWR box designs, and lever frame designs. I think there may even have been LNWR cabins with GWR frames, although I am struggling to quote example "off the top of my head".
There was a similar situation on the A&N Jt (LNWR & MR), WL/WLE Jt (LNWR & GWR), and I think WC&E (LNWR & FR Jt) also P&W Jt (LNWR & L&YR).
The other solution was to divide the work geographically, as happened on the GNR & LNWR Jt and I think on the OA&GB Jt (LNWR & GCR).