It is quite possible that multiple DX200s can interfere with each other if the full 2400 – 2483 MHz band is utilized.  Same would be true if a DX200 and Tempest base were placed in close proximity to each other (30 feet or less) that used the entire 2400 MHz permissible band.  The interference would present itself as clicks or pops as the two carriers momentarily collide with each other.
The earliest models of the DX200 could not be syncronized to work when co-located with other DX200s.  However, as of March 2006 (starting with PN G27627 Rev.A), up to four DX200's can be used side by side when 'Initialized' together.  Instructions can be found in the DX200 Operating Instruction Manual.
As of March 2009 (starting with PN G27627-3Z1 Rev. A) a Spectrum Friendly feature was added to the DX200 which allows splitting the band in half (using either low or high band).
When the DX200 and Tempest are used together both systems can be placed into opposite areas of the 2400 MHz band if required.
DX200 base stations have front panel controls to select Low, High or All:
Low 2.4 GHz band – 2401 to 2440 MHzHigh 2.4 GHz band – 2443 to 2483 MHzAll 2.4 GHz band - 2400 to 2483 MHz
Tempest base stations have menu settings to use the entire band or to select sections of the 2.4 band. 
                                           MHzBand       Chans     Start     End     Wide    Avoid 802.11b/g1                43         2400     2480      80        None2                27         2400     2450      50        113                27         2423     2473      50          14                27         2431     2480      49          1,25                15         2400     2428      28          7,8,9,10,116                15         2423     2450      27          1,117                15         2453     2480      27          1,2,3,4,5,6,7

So it seems reasonable to conclude that a current DX200 and Tempest system could live next to each other without issues if they are frequency coordinated so as to not hop over each other by only using part of the 2.4 GHz band for each system and the antennas for each system are placed a reasonable distance apart. With the DX200 in the Low band place the Tempest into Band 7With the DX200 in High band place the Tempest into Band 5