Per product specifications...
http://www.extremenetworks.com/product/a-series/# -> Specifications -> Physical Specifications
...the A4 has no native MT-RJ ports, but each A4 unit has two SFP ports for MGBIC support.
The Pluggable Transceiver Specifications datasheet (KB 9852:
http://bit.ly/1i9pjey) will show you what is supported in those SFP ports.
The MGBIC-MT01 is supported on the A4 for MT-RJ connectivity, but can handle multi-mode fiber only.
In short, with the A4 you would need to bring in some third-party adapter or patch cable in order to meld one of the A4-supported single-mode fiber MGBICs (e.g. MGBIC-07, MGBIC-08, MGBIC-LC09; all with LC connector) with an existing MT-RJ connector terminating a single-mode fiber run.
Seems that this is a wordy way of saying "no".
