In a test setup I see the build time increases.
The setup is a follows:
Job1 creates at change in 1 file, in a a new activity for each execution, and a baseline is created.
Job2 is "poll-child", picks up the new baseline, and delivers to integration.
For each time job2 runs, it takes an additional second to process. There is nothing in the build step, just a simple "echo Hello there !".

This is the console output:

[CCUCM] Allow for slave polling: false
[CCUCM] Poll for posted deliveries: false
[CCUCM] Forcing deliver: false
[CCUCM] Polling streams: childs
[CCUCM] Getting baselines for :
[CCUCM] * Stream: stream:cc1_one_int@\cc1_PVOB
[CCUCM] * Component: component:_System@\cc1_PVOB
[CCUCM] * Promotion level: INITIAL

[CCUCM] Scanning 3 streams for baselines.
[CCUCM] [01] vobadm_cc1_one_dev1 0 baselines found
[CCUCM] [02] vobadm_cc1_one 1 baseline found
[CCUCM] [03] vobadm_cc1_one_2 0 baselines found

[CCUCM] Retrieved 1 baseline:
[CCUCM] + jenkins-CreateChange2-546(Wed Aug 28 18:59:25 CEST 2013)

[CCUCM] Using jenkins-CreateChange2-546@\cc1_PVOB
[CCUCM] View root: C:\Program Files\Jenkins\jobs\First\workspace\view
[CCUCM] View tag : CCUCM_First_CCMSFTP_cc1_one_int
[CCUCM] Reusing view root
[CCUCM] Determine if view tag exists
[CCUCM] Reusing view tag
[CCUCM] UUID resulted in CCUCM_First_CCMSFTP_cc1_one_int
[CCUCM] Getting snapshotview
[CCUCM] Updating view using all modules.
[CCUCM] Starting deliver(tries left: 2)
[CCUCM] Deliver successful
[CCUCM] Pre build steps done
[CCUCM] Finished processing baseline:jenkins-CreateChange2-546@\cc1_PVOB
[workspace] $ cmd /c call C:\DOCUME~1\vobadm\LOCALS~1\Temp\hudson4148007360795646856.bat
Hello there !

C:\Program Files\Jenkins\jobs\First\workspace>rem cleartool chstream -generate stream:cc1_one_int@\cc1_PVOB

C:\Program Files\Jenkins\jobs\First\workspace>exit 0
Processing baseline
[CCUCM] Build result: SUCCESS
[CCUCM] Completing the deliver. Success.
[CCUCM] Creating baseline on Integration stream.
[CCUCM] Absolute path of remoteWorkspace: C:\Program Files\Jenkins\jobs\First\workspace
[CCUCM] Performing common post build steps
[CCUCM] Baseline jenkins-CreateChange2-546 promoted to BUILT.
[CCUCM] Baseline cc1_one_20130828_190610 is now recommended.
[CCUCM] Post build steps done
Finished: SUCCESS