its not about them not disclosing partnerships.
its that the partners are infact themselves. trading within their own platform (as both customer and service) which has prompted an investigation into possible 'insider trading'
EG if left arm tells right arm that they are going to clap their hands. together they can make alot of noise(profit) knowing when to clap together
[exchange]
/ | \
[pfm] [pfm] [pfm]
/ \ / \ / \
[c] [c] [c] [c] [c] [c]
normally an exchange doesnt know what a portfolio manager[pfm] is about to do on a market in 1seconds time
normally a portfolio manager[pfm] doesnt know what a customer[c] is about to request in 1seconds time
but what if
[exchange] -- [pfm]
/ |
[pfm] [pfm]
/ \ / \
[c] [c] [c] [c]
exchange and pfm are the same 'entity' and have no real customers in that branch/arm