Can the tracking of cross-projects link work items in different RTC instances?

there is very limited cross server linking. it is limited to Related Change Requests, which must be configured for each sharing pair of projects.

open the project on each server, (eclipse), go tp the Links tab, in the upper right, in the Associations section, click Add.

this provides the configuration of the 'Related Change Request' link.. the RTC servers must be configured as friends before this configuration will work..

note that Change Request is a pair of one way links.

FYI, the Help for linking between project areas is here http://pic.dhe.ibm.com/infocenter/clmhelp/v4r0m3/topic/com.ibm.help.common.jazz.calm.doc/topics/t_calm_link_projects.html