In principle to link 2 Eclipse matrices there are always two basic connections which have to be made between the two matricesa) Audio trunk lines (using 4wire lines, E1 , Fibre or IP) to carry the audio traffic between the matricesb) Ethernet LAN to carry the control data between the two matrices. 
Depending on the audio trunk line method used will determine the distance between the matrices
In general if your trying to go 170Km you will need to convert the trunk line from the matrix and use either the customers own infrastructure or a leased line from the local telco company

• 4wire Analogue trunk lines (can be converted to IP or E1 or ATM or ISDN, microwave…etc…)

• E1 trunk lines (can be converted to IP or E1 or ATM or ISDN, microwave….etc…)

• Fibre – cannot be converted as we use proprietary signalling – using long haul fibre transceivers we can go about 20km between matrices

The E-QUE (E1) card can provide 60 audio channels for tie lines (or Intelligent linking)  between Eclipse Median  or Omegas.We most often use third party devices to convert our E1 (G.703) stream to IP.
Devices for routing our E1 over IPIt’s possible for both 4000 and Eclipse systems to route E1 trunk lines over IP base infrastructure.Generally this solution can be configured to give low voice latencies ... esp. when compared with single channel VoIP.
We have used the following products (all with positive experience) ·         Cisco (7200 Series) ·         Verso (Net Performer SDM 9220)·         RAD  (IP-Mux)  (Newer models are available now)
Cisco are a well establish name and the client already used Cisco ... so he  just need to add one E1 card to each of his Routers. Verso provide a cost effective Router for remote offices and is flexible enough to be used for other inter-site traffic RAD have been providing their TDMoIP product for many years ... they can provide mature standalone solution as well as bigger routers. 
This solution is dated 8-Nov-2010, please check the knowledge bases for newer references