Not a fan of time tracking in legal departments, except for limited times and purposes, I question even more internal tracking of time when there are stated expectations of chargeable hours. That practice is problematic for the same reasons that chargeable hour goals at law firms ought to worry law departments (See my post of Nov. 2, 2006: chargeable hour goals in firms; and Aug. 22, 2006: chargeable hour goals in firms.).
In-house lawyers may be sloppy about tracking their time, to be sure, but the more important objection is that people bend over backwards to achieve the minimum goal and pay secondary attention to whether the client who pays for the work gets value.