Cannot set authentication tls for sipe account (pidgin works fine though)

[lyncuser]

In pidgin to connect to the lync server of my company I need to adjust the useragent to CCAPI/4.0.7577.0 OC/4.0.7577.0 and the authentication scheme to tls-dsk. This works with pidgin.

I try to do the same with bitlbee however I cannot change the authentication scheme from ntlm to tls, so the connection always fails with,

<user> acc 1 on
<root> sipe - Logging in: Connecting
<root> sipe - Login error: Incompatible authentication scheme chosen
<root> sipe - Logging in: Signing off..

<user> acc 1 set
<root> authentication = `ntlm'
<root> auto_connect = `true'
<root> auto_reconnect = `true'
<root> away is empty
<root> display_name is empty
<root> email = `'
<root> email_login = `'
<root> email_password = `'
<root> email_url = `'
<root> groupchat_user = `'
<root> nick_format is empty
<root> nick_source = `handle'
<root> password = `********' (hidden)
<root> server = `'
<root> sso = `true'
<root> status is empty
<root> tag = `sipe'
<root> transport = `auto'
<root> useragent = `CCAPI/4.0.7577.0 OC/4.0.7577.0'
<root> username = `******************************************'

Here I try to switch to 'tls' but the bitlbee server on localhost answers always with 'ntlm'

<user> acc 1 set authentication = 'tls'
<root> authentication = `ntlm'

$ dpkg -l | egrep "bitlbee|sipe"
ii  bitlbee-common                             3.2.1+otr4+20140214+devel+1011-1                    An IRC to other chat networks gateway (common files/docs)
ii  pidgin-sipe                                1.13.1-2                                            Pidgin protocol plugin to connect to MS Office Communicator

[dx]

(added code blocks to description)

Errrr... how are we supposed to test this weird protocol?