This depends.. as long as the user has permissions on the portion that he connects to it is legal. For example:
Let us say echolink node a is a 2 meter repeater and echolink node b is a 10 meter repeater and both are linked either via RF or echolink. A technician class license holder may connect to echolink node a and converse. This is because he is connecting to the repeater that his license permits him to. The fact that the repeater he is connected to happens to be linked to an HF repeater is of no concern.
To answer his question:
As a technician class license operator you have permission to all modes and all frequencies above 30 mhz. 70cm is well above 30 mhz so you have the ability to connect to it. I would say that 70% or more of echolink users hold a technician class license. HF echolink nodes are scarse in comparison to the other stations. You can use echolink freely and connect to any repeater that operates above 30 mhz. You may also connect to other PC nodes as well.
Here is another situation:
My girlfriend is a technician and I am a general. If she is at home on the computer and I am driving around mobile useing the 10 meter band. I can bring up a 10 meter echolink repeater and type in her echolink ID and connect to her. We can then converse as we would normally eventhough it is on the 10 meter band and she does not have 10 meter privileges. This is because I initiated the connection and I hold a general class license with permissions on the 10m band. I am in essence the control operator at that time.