From Mitel knowledge base:
Document ID QA1312
Title
How come my 69XX IP phones do not identify that the phone is in fail over mode?
Question
My 53XX series IP phones show a flashing cursor when in fail over mode, but my new 69XX series IP phones do not, why is that?
Answer
A decision was made to have the new 69XX series sets not identify when the IP phone is in fail over mode in the same manner as the 53XX series IP phones.
Where the phone is connected to can be identified by following the steps below.
1-Press the gear button
2-Select Status
3-Under Network General Info
scroll through the options looking for the value of the Current Call Server IP Address and this will show you were the IP phone is registered to.