You can use 90°C wire anywhere you want as long as you use it at a current rating equal to or lower then the current rating for the same size conductor based on the temperature rating of the terminal and equipment. For example 3/0 at 90°C has an ampacity of 225 amps. You can use this wire with 200 amps of load on 75°C rated equipment and at 165 amps for 60°C rated equipment. If you have 6 current carrying conductors in the raceway, you can derate from the the 90°C rating. Remember that both the equipment and terminals must be rated at 90°C to use the full 90°C rating.
As far as the DLO cable, I often use it for large DC motors that have 700 volt armatures. DLO is rated at 1000 or 2000 volts depending on the type, and it sure makes it easier to make the connections in the motor junction box. The last DC motor that I hooked up had 8 535.3kcmil DLO cables for the positive lead and 8 more for the negitive lead. I guess that its use in this type of application is a code violation, but I don't see any hazards created by its use.
Don
