The £10bn deal dominates PRWeek's latest chart, with US consultancies Abernathy MacGregor Group and Owen Blicksilver PR (fifth and sixth respectively) also having played a role.
Finsbury represents Permira Funds in the consortium alongside Citigate Dewe Rogerson (fourth).
The Texas Pacific Group, also part of the consortium, is working with Owen Blicksilver. Freescale uses Abernathy MacGregor.
Finsbury also represented construction firm John Laing as it received a £832m bid from Henderson Infrastructure Holdco.
Despite the Freescale bid rather skewing this month's results, second and third spot are occupied by agencies with no involvement in the deal. Brunswick, in second, worked on 26 deals through September. The biggest was the takeover of BOC by fellow industrial gas company Linde AG.
The German acquirer used Maitland (third) for the £8.2bn deal.
Maitland also advised on the sale of Abbey National's life insurance operation to Resolution for £360m. The purchaser used Temple Bar Advisory (eighth) in the September deal.
Brunswick worked for Investor Group on its £2bn institutional buyout of casino firm Kerzner. Investor Group also used Joele Frank Wilkinson Brimmer Katcher (ninth). College Hill (seventh) was powered by its part in the deal - Caledonia Investments used the agency for the acquisition.
Finishing off the top ten is Financial Dynamics, which handled 20 deals in September, although none grabbed more headlines than the agency's own sale to US firm FTI Consulting.
DEAL WATCH - September 2006 rankings
01. Finsbury, 11 (No. of Deals) - 18,051 (Deal Value £m)
02. Brunswick Group, 26 - 16,612
03. Maitland, 6 - 13,115
04. Citigate Dewe Rogerson, 10 - 11,549
05. Abernathy MacGregor Group, 1 - 10,011
06. Owen Blicksilver PR, 1 - 10,011
07. College Hill, 17 - 4,716
08. Temple Bar Advisory, 1 - 3,600
09. Joele Frank Wilkinson Brimmer Katcher, 2 - 3,101
10. Financial Dynamics, 20 - 3,051
Source: Zephyr published by Bureau van Dijk