Here's a quick and dirty script that proves you can share a session between pyVmomi and SUDS clients in either direction. Here's how.

share_sessions_between_pyvmomi_and_suds

#!/usr/bin/python

import argparse
import cookielib
import suds

parser = argparse.ArgumentParser()
parser.add_argument('-s', '--host', required=True, action='store', help='Remote host to connect to')
parser.add_argument('-u', '--user', required=True, action='store', help='User name to use when connecting to host')
parser.add_argument('-p', '--password', required=True, action='store', help='Password to use when connecting to host')
parser.add_argument('-o', '--port', required=False, action='store', help="port to use, default 443", default=443)
args = parser.parse_args()

url = "https://%s/sdk/vimService.wsdl" % args.host

print "Python suds..."
client = suds.client.Client(url,location=url)
si = suds.sudsobject.Property("ServiceInstance")
si._type = "ServiceInstance"
sc = client.service.RetrieveServiceContent(si)

client.service.Login(sc.sessionManager, userName=args.user, password=args.password)


def get_current_session(client):
    property_filter_spec = client.factory.create('ns0:PropertyFilterSpec')
    property_spec = client.factory.create('ns0:PropertySpec')
    property_spec.pathSet = ['currentSession']
    #property_spec.all = True
    property_spec.type = "SessionManager"
    property_filter_spec.propSet = [property_spec]
    object_spec = client.factory.create('ns0:ObjectSpec')
    object_spec.obj = sc.sessionManager
    object_spec.skip = False
    property_filter_spec.objectSet = [object_spec]
    options = client.factory.create('ns0:RetrieveOptions')
    options.maxObjects = 1
    results = client.service.RetrievePropertiesEx(sc.propertyCollector,
                                                  specSet=[
                                                      property_filter_spec],
                                                  options=options)

    def get_property(self, name):
        for obj in self.objects:
            if not hasattr(obj, 'propSet'):
                return None
            for prop in obj.propSet:
                if prop.name == name:
                    return prop.val

    results.__class__.get_property = get_property
    return results.get_property('currentSession')


current_session = get_current_session(client)

if current_session:
    print "current session id: %s" % current_session.key
    cookies = client.options.transport.cookiejar
    for cookie in cookies:
        print "cookie '%s' contents: %s" % (cookie.name, cookie.value)
else:
    print "not logged in"

# now to move the current session ID over to pyVmomi
print "now pyVmomi ... "
import pyVim.connect as connect

si = connect.SmartConnect(host=args.host,
                                user=args.user,
                                pwd=args.password,
                                port=int(args.port))

print "current session id: %s" % si.content.sessionManager.currentSession.key
pyvmomi_cookie = si._stub.cookie
print "current cookie contents: %s" % pyvmomi_cookie


VMWARE_COOKIE_NAME='vmware_soap_session'

def extract_vmware_cookie_suds(client):
    cookiejar = client.options.transport.cookiejar
    for cookie in cookiejar:
        if cookie.name == VMWARE_COOKIE_NAME:
            return '%s=%s' % (cookie.name, cookie.value)

client.__class__.extract_vmware_cookie = extract_vmware_cookie_suds

def inject_vmware_cookie_suds(client, cookie_value, domain):
    for cookie in client.options.transport.cookiejar:
        if cookie.name == VMWARE_COOKIE_NAME:
            cookie.value = cookie_value
            return

    cookie = cookielib.Cookie(0,
                              VMWARE_COOKIE_NAME,
                              cookie_value,
                              None,
                              None,
                              domain,
                              None,
                              None,
                              "/",
                              None,
                              None,
                              None,
                              None,
                              None,
                              None,
                              None,
                              None,)
    client.options.transport.cookiejar.set_cookie(cookie)

client.__class__.set_vmware_cookie = inject_vmware_cookie_suds

print "=" * 80
print "suds session to pyvmomi "

si._stub.cookie = client.extract_vmware_cookie()
print "current suds session id:    %s" % get_current_session(client).key
print "current pyVmomi session id: %s" % si.content.sessionManager.currentSession.key

print "=" * 80
print "pyvmomi to suds"

si._stub.cookie = pyvmomi_cookie
cookie_value = pyvmomi_cookie[pyvmomi_cookie.index("=")+1:pyvmomi_cookie.index(";")]
print "current pyVmomi session id: %s" % si.content.sessionManager.currentSession.key
client.set_vmware_cookie(cookie_value, args.host)
print "current suds session id:    %s" % get_current_session(client).key

Note: This work needs to be cleaned up for use in a library.