ContactAir: 4 Do328 on order, not sure about the date of order, but probably before they took CLHs F50s.
EuroCityLine: 1 Do328 (I think). Not sure about date of order, but how long has EuroCityLine been in business? Not very long... Must have been in 1995.
I didn't think that anybody remembers EuroCityLine
What kind of information do you need? I've got some information about their route network (especially about summer 1995, when STR was closed for all aircraft larger than ARJ, EuroCityLine did quite a lot of flights during these three months).
"normal" EuroCityLine flights, with MetroII (D-ICRK)
STR-RTM-STR started 02May 1995, twice daily (LP100/101 and LP106/107)
STR-MUC-STR started 22May 1995 daily (LP705/106)
STR-BLQ-STR started 22May1995 daily (LP202/203)
flights during STR runway works, with Regional Airlines SF340:
STR-HAJ-STR (LP505/506 and LP585/586)
Hope this helps. In case you need more information about EuroCityLine, just ask.