The XTS3500 is a dead product line. It was only available in conventional (no trunking), and rumour has it was only put out as an interim fix to please some 3-letter agencies who didn't like the 'wake-up' time of the XTS3000, along with wanting tighter RX specs, and didn't want to wait for the XTS5000. Call it a bastard child, if you will. Motorola's resources have been more focused on the XTS1500/2500/5000 line.
Todd