Does IAX2 support multiple registration with 1 username & pw

I am using freePBX 2.10 and 2.9 with asterisk 1.8.7
I have 10 virtual (using VMwear) PBX server. One of the server is a core PBX.
In the core PBX I have one IAX trunk with the following settings (note: i am using freepbx to create the trunk).

Trunk name: FAIL-INCOMING

Outgoing:

Incoming Settings:
USER Context: uks-outside
type=user
trunking=yes
secret=iax123
permit=192.168.0.10/255.255.0.255&10.57.0.10/255.255.0.255&192.168.100.190/255.255.255.255
deny=0.0.0.0/0.0.0.0
context=outbound-allroutes
allow=gsm&ulaw

The other 9 server either running freePBX 2.10 or 2.9. They all register to the core pbx using the username uks-outside and the password iax123. Base on what I read on forms, there is a cap on how many calls can came in at the same time because of the over size MTU. My question is, since 9 servers register to the core with the same username and password, would that be a problem related to the limited to calls going to the core?