Well I found out why it is happening and will post that here in case anyone else needs to know but I am now looking for a way, remotely, to reset a 5360's ipv4 network settings back to factory default (not all phone settings, just ipv4 like how you can when you go through the settings on the physical phone and get into ipv4 and press 0 to default it, then it reboots).
The reason it is ignoring the dhcp option 43 server settings is because the public Mitel MBG is setting a Persistent Resiliency List. Here is the tech article that explains it:
When a MiNET 53xx device powers on or reboots, it will attempt to reach a TFTP server to obtain new firmware. Once connected to a TFTP server, the set downloads and installs new software if required. When the download attempt is complete, the set then attempts to connect to an MBG, searching for nodes as follows:
Resiliency List—If the device has previously connected to MBG and received the Resiliency List (programmed using this procedure), it will search the list from top to bottom to obtain a connection.
Teleworker IP—If the device has a Teleworker IP address (programmed by pressing 7 key on bootup on most phones), it will use it to obtain a connection.
DHCP—If all other connection methods fail, the device will attempt to obtain a connection from DHCP.
The Resiliency List of MiNET fallback addresses is optional. If you do not configure it, the devices will use the values they have been programmed with or obtain an address from DHCP.
The Resiliency List supports the following features:
Up to four node addresses can be configured.
Node addresses can be in IPv4 or IPv6 format.
Node addresses can be for any MBG, not just local MBGs. However, in a clustered environment, the addresses should be for nodes in the device's own cluster zone.
Devices search the list from top to bottom (first to fourth node) until a connection is made.
This feature is useful if you need to configure failover addresses. For example, if your enterprise is switching service providers, program a Resiliency List that contains MBG's current IP address plus the one that you will be using with the new provider. Then reset the devices in order to have them download these values. When the switchover to the new service provider occurs, the devices will attempt to connect to the original address and fail, and then try to connect to the new address and succeed. After completing this process, you can remove the original address from the Resiliency List.