Large companies usually do not repair individual components, as many people with the broken N900 USB ports found out. Most of them received brand new phones, or were left with their original broken ones. From talking to people in the industry, the way electronics are manufactured is as follows (correct me if I'm wrong, those I spoke with were building custom PCBs, not full devices):

- Company A designs a device (e.g. smartphone) in full detail.
- Specialized company B creates fully functioning prototypes, sometimes at a cost of thousands per unit based on the Company A design, since every single component has to be hand made
- Once testing is complete on the prototypes, Company A either contracts company C to fully manufacture the device (like Apple contracts Foxconn to manufacture the iPhone) OR issues several contracts for individual components to companies C-Z, and then assembles the components in-house.

So Nokia probably does not have a specialized lab with technicians dedicated to repairing individual N900 systemboards, at least not on a scale capable of dealing with thousands of broken phones a day across their entire range of devices.

Proper reflowing requires VERY expensive equipment if you want it done professionally with a low failure rate. I'll admit my suggested method has a high failure rate, but it does work most of the time. And since your phone is fubared anyway, it's worth the risk.