Hi Francisco,
You're right. You need a SIP card for your uplinks if you want to apply the xconnect to an SVI interface.
You could try creating a trunk for VLAN 3 and 33 between PE3 and PE4. Assuming all the servers are connected to PE3 (there are 2x PE3 on your drawing ;-) ), you could apply the xconnect on PE4 trunk interface only to PE1 as primary and PE2 as secondary:
xconnect 192.168.124.1 10 encapsulation mpls
backup peer 192.168.124.2 20
HTH
Laurent.